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| Social
Theridiids - Phylogenetic Patterns, Processes, and Predictions |
|
Author
|
Institutions
|
|
Ingi
Agnarsson
|
George
Washington University, Washington DC |
| Smithsonian
Institution, Washington DC |
|
|
Abstract:
Theridiids are particularly interesting for studying spider
sociality. The majority of social spider species are theridiids,
and representatives of the family show the entire spectrum
of web sharing, ranging from short term maternal care (e.g.
Theridion), to periodic or permanent social behavior
(most Anelosimus, some Achaearanea and Theridion),
and kleptoparasitism (e.g. Argyrodes). Major questions
surrounding spider sociality include: the origin of quasisocial
behavior (e.g. via aggregations around abundant resources
or temporal extension of maternal care), its phylogenetic
distribution (e.g. single vs. multiple origins, origins clumped
or randomly distributed), and how different forms of web sharing
(e.g. sociality and kleptoparasitism) may be related. To investigate
such questions I present a cladistic analysis of 61 theridiid
taxa, based on 242 morphological and behavioral characters.
The resulting phylogenetic hypothesis implies the following:
1) sociality in theridiid spiders evolved as a temporal extension
of maternal care, 2) quasisociality (<10 species in total)
originated independently no less than four times within Theridiidae;
by contrast, web sharing evolved once in the diverse clade
of kleptoparasites (>200 species), 3) social instances
are non-randomly clustered among distal theridiids, suggesting
a common cause, 4) kleptoparasitism and sociality may be related
as alternative modifications of maternal care. My phylogenetic
hypothesis, furthermore, predicts that maternal care may be
much more widespread and common than currently entertained
and that social behavior will be discovered in several taxa
whose behavior is currently unknown. One such prediction was
confirmed by the discovery of the first social Anelosimus
in Africa.(Added 6/ 12 / 2003)
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| Progress
in Tetragnathid Phylogenetics with Emphasis on the "Metinae
Problem" (Araneae, Tetragnathidae) |
|
Author
|
Institution
|
| Fernando
Alvarez |
George
Washington University |
|
|
Abstract:
Simon originally defined the tetragnathid subfamily
Metinae as comprising "all forms intermediate between
Tetragnatha and Nephila"; This definition
has obscured the higher level systematics of Tetragnathidae
for more than one century. The phylogenetic relationships
of metines are crucial to understand the evolutionary history
of tetragnathid spiders. The cladistic analysis of Hormiga
et al. (1995), based on 22 taxa and 61 characters, found metines
to be paraphyletic with respect to tetragnathines, and nephilines
sister to a clade including all remaining tetragnathid taxa.
This presentation reports recent progress towards a better
understanding of the phylogenetic relationships of metines.
The cladistic analysis of a matrix of 42 species of tetragnathids
(plus nine outgroups) and 117 characters scored (morphological
and behavioral) corroborated the monophyly of Tetragnathidae,
Nephilinae and Tetragnathinae, as well as the paraphyly of
"Metinae"; (the latter represented by 16 species).
Traditional metines comprise two lineages: 'Leucaugines' and
'Metines sensu stricto.' The relationships of these
two clades and the synapomorphies that support these lineages
will be discussed. (Added 6 / 18 / 2003)
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| Running
Speed In The Wolf Spider Pirata sedentarius: Between-Sex
Variation And A Cost Of Leg Autotomy |
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Authors
|
Institutions
|
| Pasha
Apontes |
SUNY
Fredonia, Fredonia, N.Y. |
|
Christopher
A. Brown
|
Tennessee
Technological University,
Cookeville, TN |
|
|
Abstract:
Leg autotomy in spiders is a relatively common occurrence
resulting from agonistic interactions with predators or conspecifics.
While autotomy has immediate benefits, due to enhanced survival
probability, it also potentially decreases future fitness.
One possible cost of losing a leg is a reduction in burst
running speed, which may affect prey capture and predator
avoidance behaviors in wandering spiders. We examined running
speed in intact and autotomized Pirata sedentarius,
a wolf spider commonly found in moist cobble zones, from two
stream banks in New York. Autotomy was fairly common in the
field, with 18.8% and 22.2% of spiders missing at least one
leg at our two sites. Females were relatively heavier than
males and ran significantly faster. Intact spiders, both males
and females, ran significantly faster than spiders missing
a leg. We found no difference in speed between spiders which
had lost a leg in the field and spiders for which we removed
a leg in the laboratory. Heavier females ran significantly
faster than lighter females in pre-autotomy trials, but mass
did not affect female speed following autotomy. Male running
speed was unaffected by mass. Our results suggest that leg
loss is potentially costly to both male and female P. sedentarius,
and does not support the "spare leg" hypothesis
of Guffey (1998. J. Arachnol. 26: 296-302). (Added 5
/ 15 / 2003)
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| Sociality
Buffers Against Inbreeding Depression In A Subsocial Spider |
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Authors
|
Institutions
|
| Leticia
Avilés |
Dept.
of Zoology, University of British Columbia, Vancouver,
Canada |
|
Todd
Bukowski
|
Center for Insect Science, University of Arizona, Tucson,
USA. |
|
|
Abstract:
Social spiders are unusual among social organisms
in being highly inbred--males and females mature within their
natal nest and mate with each other to produce successive
generations. We hypothesize that such inbred social systems
originated under conditions where benefits of group living
were sufficiently strong to overcome inbreeding depression
in the transition from an outbred ancestral state. As a window
into such conditions, we have been exploring the fitness consequences
of group living, inbreeding, and dispersal in inbred social
and outbred subsocial species in the genus Anelosimus.
In the subsocial spider Anelosimus cf. jucundus in
southern Arizona we examined the consequences of artificially-imposed
inbreeding on various components of fitness in spiders raised
under natural conditions. We found that inbreeding depression
was only evident during the solitary phases of the spider's
life cycle. Prior to dispersing from the maternal nest, offspring
from inbred and outbred clutches did not differ in size or
survival probability. Instead, fitness during these stages
was influenced primarily by ecological and demographic factors
such as lifespan of the mother, number of siblings in the
group, and distance to a creek. Following dispersal, however,
inbred spiders developed more slowly and reached a smaller
size. We suggest that a similar buffering effect of group
living may have facilitated the origin of inbred social systems
in the genus. (Added 6 / 15 / 2003)
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| Phylogeography
of the Desert Spider, Agelenopsis aperta: Testing
Predictions Based on the Fossil Record |
|
Authors
|
Institution
|
| Nadia
A. Ayoub |
University
of Tennessee, Knoxville, TN |
|
Susan
E. Riechert
|
|
|
Abstract:
Over the past two decades phylogeographic data, or the geographic
distribution of gene lineages, has been increasingly used
to infer historical events such as population fragmentation
or range expansion. Unfortunately, most phylogeographic studies
develop post-hoc explanations for observed patterns rather
than use the genetic data to test a priori hypotheses. These
a priori hypotheses can be developed from paleoclimatic, geologic,
ecological or comparative phylogeographic data. For instance,
fossil arthropod and plant data from arid southwestern United
States during the last glacial maximum indicate that many
desert organisms were restricted to lower elevations and latitudes
than their modern day distributions. The desert spider,
Agelenopsis aperta, currently exhibits a wide range throughout
the southwestern United States but is limited to areas below
6000 feet. Based on the fossil evidence and the modern day
elevational limit of A. aperta we hypothesized that
this desert spider has been restricted to lower elevations
and latitudes during glacial maximums and has only recently
expanded its range to the modern extent. We tested this hypothesis
by comparing observed patterns of mitochondrial DNA sequence
variation to predicted patterns under various historical scenarios.
Preliminary analysis shows support for a recent range expansion
event but the evolutionary history of A. aperta populations
appears to be more complex than can be predicted from the
fossil record alone.(Added 6 / 16 / 2003)
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| What
People Think About Spiders in Russia |
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Authors
|
Institutions
|
| O.P.
Bartosh |
International Scientific Center "Arktika",
Magadan, Russia |
|
T.
A. Karpenko
|
Department
of Employment of the Population, Magadan, Russia |
|
|
Abstract:
It is rather interesting for people engaged in the study of
spiders to learn what common people know about spiders. For
this purpose, a questionnaire was developed and a statistical
investigation was made among the inhabitants of Northeast
Russia. The questionnaire was given to more than 200 people
with various levels of education, and between the ages of
15 and 65 years old.
The questionnaire
that was used included 18 multiple-choice questions. The questions
concerned the way spiders live and their physical characteristics.
The questions also examined the personal attitude, of the
person completing the questionnaire, toward spiders and their
opinion of arachnologists and others who study spiders.
An analysis of
the answers to the questionnaire has shown that 96% of the
people know that spiders are invertebrate animals. However,
only 60% know that spiders have 8 legs, the other 40% of the
people thought, that spiders have 6 legs. Almost all people
know that spiders build their webs from their own silk glands.
Only 1% has answered that spiders use the wool of animals.
The majority of the people questioned, confirmed that some
kind of spiders are dangerous to man and live in family couples.
They also approved the fact that the male spider, during the
mating period, entices the female spider to his web. Some
of the people think that spiders feed on carrion and blood.
The majority of the people participating in this study have
a positive attitude toward spiders. However, many of the women
surveyed are afraid of them and have a sense of fastidiousness.
All people consider that spiders are useful and important
animals in the natural environment, but many of them killed
spiders in their childhood. Most of the people questioned
thought that arachnologists are unusual and strange people,
however necessary to science. The results of the questionnaire
about spiders were considered interesting and unexpected.(Added
5 / 23 / 2003)
|
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| The
Effect Of Predator Hunger On Chemically-Mediated Antipredator
Responses And Survival In The Wolf Spider Pardosa milvina
(Araneae: Lycosidae) |
|
Authors
|
Institutions
|
| Ryan
D. Bell |
Susquehanna
University, Selinsgrove, PA |
|
Ann
L. Rypstra
|
Miami
University, Hamilton, OH |
| Matthew
H. Persons |
Susquehanna
University, Selinsgrove, PA |
|
|
Abstract:
The wolf spider, Pardosa milvina, exhibits antipredator
behavior when detecting silk and excreta from a larger co-occurring
wolf spider, Hogna helluo. Since the quantity and quality
of silk and excreta may vary with the hunger state of the
predator, we tested if cues from hungry vs. satiated Hogna
would influence Pardosa activity level and survival.
Pardosa activity was measured on substrata containing
chemical cues from 1) a satiated Hogna, 2) a Hogna
withheld food for 2 weeks, or 3) a control consisting of a
blank test container (N = 20/treatment). Pardosa response
was recorded on each substratum over a 30-min period using
video-tracking equipment (Videomex I). We then measured Pardosa
survival in the presence of live hungry and satiated Hogna
on each respective substrate treatment or a blank control
substrate in a fully factorial design. Results indicate
Hogna cues significantly reduced Pardosa activity
level and that Pardosa show significantly less activity
in the presence of cues from a hungry Hogna than a
satiated one. Predator hunger state and substratum type significantly
affected Pardosa survival in the presence of live Hogna.
However, cues from hungry vs. satiated Hogna resulted
in no difference in Pardosa survival nor was there
a significant interaction between Hogna hunger state
and substratum type on Pardosa survival. In summary
Pardosa can discriminate between hungry versus satiated
predators based on silk and excreta cues alone, but differences
in behavior as a result of this discrimination did not translate
into increased survival in the presence of a live predator.
(Added 5 / 14 / 2003)
|
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| Did
Bolas-Hunting Spiders Evolve Through Gradual Web Reduction? |
|
Authors
|
Institution
|
| Todd
A. Blackledge |
University
of California, Riverside, CA |
| Cheryl
Hayashi |
|
|
Abstract:
Moth hunting bolas spiders construct some of the most specialized
webs found within the Araneidae. These highly reduced webs
are thought to have evolved through a gradual reduction of
the orb web within the Cyrtarachninae, which accompanied an
increased specialization upon male moths as prey. However,
this classic evolutionary story has never been empirically
tested. We used both mitochondrial (16S and COI) and nuclear
(H3 and 18S) DNA sequence data to construct a phylogeny of
genera within the Cyrtarachninae and to test the monophyly
of these moth specialists using several putative araneid genera
as outgroups. We also compare our results with the current
phylogenetic hypothesis of araneid relationships based upon
morphology and behavior. . (Added 6 / 12 / 2003)
|
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| A
Newly Introduced Jumping Spider (Myrmarachne formicaria)
in North America |
|
Author
|
Institution
|
| Richard
Bradley |
The
Ohio State University at Marion, Ohio |
|
|
Abstract:
The large genus Myrmarachne (Araneae: Salticidae)
includes over 200 species, with representatives on each biogeographic
region except the Nearctic. A population of Myrmarachne
formicaria has been discovered in northeastern Ohio. There
is reason to believe that this species, which is widespread
in Europe, is a recent accidental introduction to this area.
This species seems to be well established, having been found
with increasing frequency over the past three years. A resident
of Warren, Trumble County, Ohio first reported noticing this
odd ant-mimic around her residence during the summer of 2000.
The first specimen record was obtained from the same locality
on 16 August 2001. Subsequently, specimens have been found
in neighboring Portage County. The species appears to be common
in a variety of situations, including occasionally inside
buildings. (Added 6 / 17 / 2003)
|
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| Wandering
the Range: Ground-Dwelling Spiders of the Sevilleta Nwr,
New Mexico 1990-2000 |
|
Author
|
Institution
|
| Sandra
L. Brantley |
Museum
of Southwestern Biology, University of New Mexico, Albuquerque |
|
|
Abstract:
New Mexico’s climate is strongly affected by
ENSO (El Nino Southern Oscillation) events, usually resulting
in increased (El Nino) or decreased (La Nina) average winter
precipitation. Arthropods are among the fauna monitored at
the Sevilleta National Wildlife Refuge for changes in species
and abundance that may be due to ENSO. I examined data from
12 predaceous families (9 spiders, 1 scorpion, 1 solpugid
and 1 centipede) from 1990-2000 for relationships between
these groups with rainfall in general and ENSO in particular.
I used a "water year," from Oct 15 of one year to
Oct 15 of the next, which described local growing seasons
better than a calendar year. During this time there were 5
El Nino years, 2 La Nina years and 4 medial years. Arthropod
data came from species counts from pitfall traps operating
continuously since 1989 and collected at 2-month intervals.
The traps were placed in three habitat types: desert grassland,
creosotebush shrubland and pinon-juniper woodland. I used
detrended correspondence analysis (DCA) to assess how well
these generalist predators differentiated among habitats (very
well) and years (not well). I used correlation analysis to
assess the relationship for each family with precipitation
at each site. Here the independence of family responses became
clearer: at all sites gnaphosids and thomisids showed no correlation
with precipitation, but lycosids did. Responses for the corinnids
and dictynids varied by site. These assemblages were robust
over this period, suggesting that the ENSO events were not
severe enough to greatly influence community structure or
function. (Added 5 / 20 / 2003)
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| Testing
Biodiversity Theory With Ground-Dwelling Spiders: Effects
Of Productivity And Disturbance |
|
Authors
|
Institutions
|
| Chris
Buddle |
McGill
University, Montreal, Quebec |
|
Ann
Rypstra
|
Miami
University, Hamilton, Ohio |
|
|
Abstract:
Understanding what determines species diversity is a central
ecological question. We tested whether ground-dwelling spider
diversity is governed by the interaction between productivity
and disturbance, as depicted by Huston’s Dynamic Equilibrium
Model. We created circular straw mulch ‘habitat islands’
(0.5 m radius) on top of 2 x 2 m areas along a disturbance
gradient: old-growth forest floor (lowest disturbance), no-till
soybean fields, soybean fields tilled once, and soybean fields
tilled twice (highest disturbance). Productivity was manipulated
by adding compost beneath the straw mulch, which directly
increased in the primary prey of spiders (Collembola) but
did not affect spider diversity. The disturbance gradient,
however, significantly affected diversity, and the intermediate
disturbance hypothesis was supported. The forest-floor had
the lowest spider diversity, and may be a dominance-controlled
community. Patterns in soybean fields suggest the colonization-competition
trade-off may be partially responsible for patterns in spider
diversity. (Added 5 / 16 / 2003)
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| Sperm
Competition Mechanisms May Benefit Female Orb-Weaving
Spiders, Micrathena gracilis |
|
Author
|
Institution
|
| Todd
C. Bukowski |
Center
for Insect Science, University of Arizona |
|
|
Abstract:
Multiple mating by females and the ensuing sperm competition,
often selects for mechanisms that either prevent other males
from releasing sperm or that displace previous males’
sperm. Because sperm competition occurs within the female’s
reproductive tract, it is thought that females should influence
which mechanisms succeed. I show here that the socially polyandrous
but typically genetically monandrous spider, Micrathena
gracilis, accrue significant weight-gain benefits by mating
with both reproductive tracts soon after molting to adulthood.
In this species males seek out females approaching the final
molt, and females mate soon after molting. The act of mating
usually alters the female reproductive tract in ways that
effectively limits sperm release by subsequent males. I released
individually marked females of various mating histories into
an experimental forest plot in which all males had been excluded.
I then followed their movements through the forest and measured
their weight gained over time. Virgin and one-side virgin
females built their webs higher above the ground and moved
more often than non-virgin females. Non-virgin females gained
weight more than three times as fast as virgin and one-side
virgin females, an effect likely mediated, in part, by reduced
foraging efficiency in the latter groups. Among non-virgin
females, those with a genetically monandrous reproductive
strategy gained more weight than females with the more rare
genetically polyandrous strategy. I suggest that the mechanism
that limits sperm release by subsequent males may underlie
the effects of mating on weight gain. (Added 6 / 18
/ 2003)
|
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| Corn
Plants Near Discrete Habitat Refugia (Small Straw Piles)
in Conventionally-Tilled Fields Show Increased Growth,
and Reduced Insect Damage |
|
Authors
|
Institution
|
| Alan
B. Cady |
Depart.
of Zoology and Depart. Botany, Miami University, Oxford,
Ohio |
| Jon
Tyson |
|
|
Abstract:
The generalist predatory arthropods (GPAs)occupying crop fields
have great potential as agents of biological control. The
endemic species comprising this predator community are finely
adapted to their specific microclimates and communities. Unfortunately,
conventional tillage and harvesting operations are cyclical
and destructive events, forcing the native generalist predator
community to re-colonize these fields each year. Supplying
discrete habitat refugia (small straw piles; 1m X 0.5m) is
a simple and inexpensive means of reducing the impact agricultural
techniques exert on populations of predatory arthropods in
agroecosystems by providing them places to live and reproduce
in the fields before the crops grow and mature. Previous experiments
with such refugia in soybeans showed these straw piles harbored
greatly increased carabid beetle and spider populations. Considering
the drier, more open growth structure of corn, it was hypothesized
that the influence of refugia in corn probably would be greater
than for soy. Experiments with straw refugia in six one-third
hectare conventionally-tilled fields found higher corn yields
and plant growth near refugia, and insect damage was less
for plants near refugia than at control sites. When larger
GPAs were excluded from refugia, plants near those sites had
similar growth and insect damage as plants near unscreened
regugia. Comparisons of soil nutrients in refugia vs. control
sites showed no significant differences, eliminating the possibility
of a "fertilizer effect" influencing corn growth
and yield. Further larger-scale tests are required. This easy
and cheap technique has potential to help farmers increase
yields with little effort and expense. (Added
6 / 12 / 2003)
|
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| A
Banding Technique For Studying Spiders In Pecan Canopies |
|
Authors
|
Institution
|
| Alejandro
Calixto |
Department
of Entomology, Texas A&M University, College Station,
TX |
|
Allen
Dean
|
|
Bill Ree |
| Lisa
Brooks |
| Marvin
Harris |
|
|
Abstract:
Corrugated cardboard band refuges were used to determine phenology
and density of spiders throughout the year on pecan foliage.
Two hundred bands (10 per tree on 20 trees, with each band
2.5"x5", folded over a twig and held by a clothespin)
were attached to the limbs at heights between 1.6- 2 m. They
were left for 7 days, collected, placed into ziplock bags
and replaced; the bags were numbered by tree and returned
to the lab where they were frozen for later analysis. In the
lab, each band was inspected and all spiders and other arthropods
were counted. A total of 20,358 spiders including 63 species
within 17 families were collected using this banding technique.
Hibana sp. (27%), Trachelas mexicanus (10%),
Philodromus sp. (8%), Eris sp. (5%) and Hentzia
sp. (5%) were the most common species encountered. Spiders
are present year round. Phenology consisted of an increase
in number across the year and a reduction, but not disappearance,
during the winter. Increases in numbers were observed in September
and December suggesting an increase in "ballooning"
behavior as a response to the oncoming winter. This method
provides an efficient and inexpensive technique to study spiders
in pecan tree canopies. (Added
6 / 17 / 2003)
|
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|
Prey Selection By The Red Widow Spider (Araneae: Theridiidae)
|
|
Authors
|
Institutions
|
| James
E. Carrel |
Division
of Biological Sciences
University of Missouri-Columbia |
|
Mark
Deyrup
|
Archbold
Biological Station, Lake Placid, FL |
|
|
Abstract:
To ascertain the prey of the red widow spider, Latrodectus
bishopi, hereafter called "RWS", we collected
arthropods trapped in webs of 30 adult females located in
native oak-palmetto scrub at the Archbold Biological Station
after dawn and before dusk for 5 consecutive days in early
spring (March, 1989) and in late spring (May, 2003). We found
that RWS females in early spring fed predominantly on nocturnally
captured coleopterans (80% of prey items), but in late spring
day-active hymenopterans were added to the RWS diet. Analysis
of arthropods collected in aerial-interception traps operated
at different heights in Florida scrub in winter, summer, and
fall suggested that the predilection of RWS for beetles was
a true specialization: coleopterans comprised only between
5 and 18% of the catch. Moreover, unlike hymenopterans and
other arthropod taxa, we found significantly more beetles
in traps operated at 1.5 and 1 m elevation, where RWS webs
were located, than in traps at 0.5 m. Finally, statistical
analysis of patterns of prey captured by individual RWS females
showed that the process was infrequent (£
0.4 prey/spider/day) and random. (Added 5 / 23 / 2003)
|
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| Gastrulation
and Inversion in Spider Development |
| Authors:
R. Crystal Chaw and Steven D. Black |
|
Institution:
Kleinholz Biology Laboratories,
Reed College, Portland, Oregon
|
|
|
Abstract:
No one model of gastrulation in spiders is clearly supported
by data in the literature. In embryos of Zygiella x-notata,
we observed formation of an extracellular-matrix protrusion
not described in other species. This ‘nipple’ forms
prior to cell involution and migrates posteriorly, presumably
reflecting movements of superficial cells. Next, we identified
a distinct site of involution, the cumulus, which is a swelling
several cell layers thick that forms near the origin of the
nipple. Superficial cells move via the cumulus into the interior
as the cumulus migrates posteriorly during gastrulation. After
gastrulation is complete, the internalized cells participate
in the formation of the germ band, which is the primordium
of the ventral aspect of the spider. At this point the embryo
undergoes a massive morphogenetic movement called inversion.
The germ band splits along the ventral midline and the two
halves migrate away from each other to rest on opposite sides
at the equator. After the halves have reached their equatorial
endpoints, cells emerge from the halves to close the embryo
dorsally while a cell sheet migrates from the posterior end
of the embryo to close it ventrally. Despite being a definitive
characteristic of spider development and one of the longer
cellular migrations known in axis formation, inversion has
not been studied beyond its description. Our preliminary investigation
of possible cytoskeletal mechanisms underlying inversion used
confocal imaging of tubulin and actin, and microinjection
of microtubule and microfilament inhibitors. We demonstrate
that inversion does not continue when either system is poisoned.
(Added 4 / 24 / 2003)
|
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| Contrasting
Patterns of Genetic Structuring in Homalonychus (Homalonychidae)
from the Desert Southwest |
|
Authors
|
Institution
|
| Sarah
Crews |
Department
of Biology, San Diego State University, San Diego, CA. |
| Marshal
Hedin |
|
|
Abstract:
The genus Homalonychus includes two species
(H. selenopoides & H. theologus), both distributed
in desert habitats of southwest North America. Prior studies
indicate that H. selenopoides consists of a single
genetic lineage, but that H. theologus is separated
into two deeply-divergent mitochondrial lineages (H. theologus
"northern" and "southern"). We have compared
the population history and genetic structuring of H. selenopoides
and H. theologus "northern" using DNA sequence
data. These two lineages are very closely related, show few
apparent ecological differences, and in most places are separated
only by the narrow strip of the Colorado River, although no
apparent geographic barrier exists in the northern Mojave
Desert (vic. Death Valley). Unless landscape or regional histories
have been very different, we might expect these spider lineages
to exhibit similar patterns of genetic structuring. This expectation
is not corroborated by our data. Instead, sequence data indicate
that H. selenopoides is highly genetically-structured
across the eastern Sonoran desert. Most haplotypes are geographically
confined, and divergent from haplotypes from other sampling
sites, suggesting long-term population fragmentation. Conversely,
the H. theologus "northern" lineage shows
a mosaic population genetic structure. More southerly regions
are genetically structured, much like H. selenopoides.
However, northern populations of this lineage show a pattern
of genetic structuring consistent with recent range expansion,
with a few closely-related haplotypes spread broadly over
space. This apparent N > S range expansion is most obvious
in the Mojave Desert, where the "northern" H.
theologus lineage may actually be displacing the H.
selenopoides lineage.(Added 5 / 23 / 2003)
|
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| Taxonomic
Diversity of Jumping Spiders in Trinidad and Tobago |
|
Authors
|
Institutions
|
| Bruce
Cutler |
University
of Kansas, Lawrence KS |
|
G.
B. Edwards
|
Florida
State Collection of Arthropods, Gainesville FL |
|
|
Abstract:
Trinidad and Tobago consists of two islands on the continental
shelf off the northeast coast of Venezuela. Last year we published
a list of the salticid fauna of this country (Living World,
p. 39-44, 2002), noting 117 species. The majority of specimens
were collected in the lower montane rain forest of the Northern
Range of Trinidad. More intensive collecting in other habitats
should produce more taxa. The number of species in eight salticid
subfamilies was determined. Two non-taxonomic catagories were
also enumerated, antlike and introduced species. The resulting
percentages were compared to other New World regions with
a relatively well catalogued salticid fauna. Unfortunately
no comparable species lists exist for Venezuela or the Guianas
so it is not possible to make a comparison to the nearest
continental areas. In Trinidad and Tobago the largest subfamily
is the "Freyinae" (not formally defined) with 19%
of the species, followed by the Dendryphantinae with 15% and
the Euophryines with 12%. Freyines are a speciose Neotropical
group reaching their greatest diversity in equatorial South
America. Dendryphantines are worldwide with most species in
the New World. Euophryines are another worldwide subfamily
with greatest diversity in the tropics. In comparison on the
Caribbean islands (-Trinidad and Tobago) Euophryinae are the
largest subfamily with 24% of the species. Freyines only constitute
3% of the species. The diversity of salticids of Trinidad
& Tobago more closely resembles that of mainland South
America than of the northern Caribbean. (Added 5 / 30
/ 2003)
|
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| Natural
History, Mating Behavior and Sperm Release in the Haplogyne
Glenognatha emertoni (Araneae: Tetragnathidae) |
|
Author
|
Institution
|
| Anne
Danielson-Francois |
University
of Kansas, Lawrence, KS. |
|
|
Abstract:
Glenognatha emertoni (Simon) is a small tetragnathine
orb-weaver whose habits are unknown and which has previously
been collected under rocks near streams in southern Arizona
and New Mexico. Field observations revealed that adults are
commonly found in vegetation alongside streams, rarely under
rocks, and do not emerge from their retreats until dusk. Adult
individuals and penultimate instar spiders raised to adulthood
were used to examine sperm release and mating behavior in
the laboratory. Unlike most other orb-weaving spiders studied,
the number of sperm released and overall duration of copulation
are not influenced by female mating history in Glenognatha
emertoni. Male G. emertoni release equivalent numbers
of sperm to virgin and non-virgin females, a pattern also
found in a related haplogyne spider, Tetragnatha versicolor.
Males have large ejaculates ranging from a half-million to
one-and-a-half million sperm. Males transfer more than three-quarters
of their ejaculate, on average, to females; these sperm potentially
compete with other males' sperm in the fertilization of a
clutch of approximately 15-30 eggs.(Added
5 / 20 / 2003)
|
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| Spiders
in Texas Pecans |
|
Authors
|
Institutions
|
| Allen
Dean |
Texas
A&M University, Dept. of Entomology, College Station,
TX |
|
Alejandro
Calixto,
|
Texas
Cooperative Extension, College Station, TX |
| Bill
Ree |
| Marvin
Harris |
Texas A&M University, Dept. of Entomology, College
Station, TX |
|
|
Abstract:
Spider fauna in pecan orchards has been sampled using
different collection techniques to determine relative abundance
and distribution through time. Spiders were sampled using
pitfall traps, corrugated cardboard band refuges and other
methods like hand collection. Information presented is intensive
sampling at two locations (Comanche Co. is arid and Robertson
Co. is more humid) in Texas. The most common spider species
occurring in the pecan agroecosystem, and where they were
found (trunk, leaves, nuts, ground, etc) is presented. These
predators are a significant component of the pecan agroecosystem.
Their conservation will contribute to better biocontrol in
agricultural systems and to preserving biodiversity in the
environment. (Added 6 / 17 / 2003)
|
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| The
Effects of Size, Sex, and Reproductive Condition on Thermal
and Desiccation Stress in a Riparian Lycosid Spider (Pirata
sedentarius) |
|
Authors
|
Institutions
|
| Jill
DeVito |
Miami
University, Ohio |
|
Daniel
R. Formanowicz, Jr.
|
University
of Texas at Arlington |
|
|
Abstract:
Within a species, physiological tolerances and thermoregulatory
behaviors may vary among ontogenetic stages or between sexes.
Such different tolerances can strongly affect the ecology
and life history of a species. In a laboratory study, we tested
the hypothesis that Pirata sedentarius Montgomery 1904
are differentially susceptible to thermal/desiccation stress
by size and sex. As predicted, male adults were more susceptible
to thermal/desiccation stress than females. Unexpectedly,
however, juvenile spiders survived longer under thermal/desiccation
stress than adults. Furthermore, female adults without egg
sacs displayed a trend toward higher thermal/desiccation tolerance
than females carrying egg sacs. These results suggest that
for P. sedentarius, microhabitat preferences and/or
thermoregulatory behaviors may change over the course of development,
and may vary 1) between sexes and 2) between females with
and without egg sacs. (Added 5 / 14 / 2003)
|
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| Seismic
communication in a courting male jumping spider (Araneae:Salticidae) |
|
Authors
|
Institutions
|
| Damian
Elias |
Cornell
University |
|
Andrew
Mason
|
University
of Toronto |
| Wayne
Maddison |
University
of Arizona |
| Ronald
Hoy |
Cornell
University |
|
|
Abstract:
While research on spiders has long shown the importance of
vibrations in communication, jumping spiders (Family: Salticidae)
differ from most spiders in that they are visual "specialists",
with vision playing a prominent role in their communication
behaviour. We now show that one species of jumping spider,
Habronattus dossenus, also exhibits a surprising complexity
of signalling behaviour in the vibratory (seismic) modality.
We videotaped courtship behaviour and recorded seismic signals
of males using laser vibrometry and observed that each prominent
visual signal is accompanied by a seismic component. Using
synchronous high-speed video and laser vibrometry we observed
that only one seismic signal component was produced concurrently
with visual signals, with most signals occurring independently.
In order to test the independence of visual and seismic signal
components and identify possible sound production mechanisms,
we performed several signall manipulation experiments where
we attempted to mute males. These experiments suggest that
three independent mechanisms are used to produce seismic signals,
and that the precise temporal coordination of visual and seismic
signals is not due to a common production mechanism. The extensive
use of complex, multicomponent seismic signals orchestrated
with intricate movements of ornamented appendages adds a new
dimension to jumping spider communication.(Added 6 /
12 / 2003)
|
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| Description
Of Populations Of The Colonial Orb-Weaver Parawixia
bistriata In Different Habitats |
|
Author
|
Institution
|
| Florencia
Fernández Campón |
Department
of Ecology and Evolutionary Biology, University of Tennessee |
|
|
Abstract:
Parawixia
bistriata
(Araneidae) is a colonial orb-weaver that occurs from wet
forests to semiarid habitats in subtropical and temperate
regions of South America. In order to examine the effect of
prey levels on colony size I studied colonies under different
prey conditions in populations from the Dry and Wet Chaco
in northern Argentina (referred as dry and wet sites, respectively).
I further examine whether these differences in prey levels
were translated into any difference in development of spiders
that could affect fecundity. Censuses conducted during the
spring-summer season 2002 showed that in colonies comprised
by 6th instar individuals prey availability is not positively
correlated to colony size, but shows the opposite trend. Colony
size was larger in the dry sites, but within-habitat variation
in colony size was similar between habitat types. Life cycle
stages occurred two months later in the dry than in the wet
sites. Results from transplanted colonies suggest that this
delay in stages is due to differences in prey availability.
In contrast, mean spider mass of 6th instar individuals did
not differ between habitats. The number of eggs/sac produce
by female showed the same pattern as spider mass. When reciprocal
transplants of colonies were performed, the changes in local
conditions (most probably prey) were reflected in a larger
number of eggs/sac in colonies transplanted to wet sites,
and fewer eggs/sac in colonies transplanted to dry sites.
These results suggest that prey levels do not affect aggregation
behavior in P. bistriata in the direction showed by
other species (larger colonies under high prey conditions).
However, even though lower prey levels might be delaying development
in dry populations, native individuals from dry sites seem
to be adapted to local prey conditions and, in terms of reproduction,
are as successful as populations under higher prey conditions.
(Added
6 / 15 / 2003)
|
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| Metasoma
of Orthochirus (Scorpiones: Buthidae): Are Scorpions
Evolving a New Sensory Organ? |
|
Authors
|
Institutions
|
| Elizabeth
V. Fet |
Marshall
University, Huntington, WV |
|
David
Neff
|
| Matthew
R. Graham |
| Victor
Fet |
|
|
Abstract:
A peculiar array of cuticular pits, with a single socketed
seta emanating from each, is observed ventrally and laterally
on the posterior segments of metasoma in a few Buthidae (Scorpiones),
including all species of the widespread Old World desert genus
Orthochirus Karsch. SEM investigation shows those pits
adorned with variable size setae, which exhibit microanatomical
features characteristic for chemoreceptors (curved shape,
end pore). Orthochirus metasoma at SEM magnifications
from 15x to 7,500x is illustrated. Observations in nature
(Central Asia) show an unusual rest/defense posture in
Orthochirus, with metasoma positioned flat on the dorsal
side of mesosoma, its small telson folded in a groove, and
ventral surface of the metasomal segment V forming a "face
shield". The observed side-to-side metasomal motion during
prey search also seems to agree with a possible special functional
role. We suggest that the up-and-forward facing (in rest posture)
ventral/lateral surfaces of posterior metasoma in Orthochirus
and related buthid genera could be used as a chemosensory
array, analogous to insect antennae. Or, quoting Brownell
(2001) on arachnid chemoreception, "God has a plan after
all!".(Added 6 / 12 / 2003)
|
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| A
Behavioral Investigation Of Male-Male Interactions In
Phrynus marginemaculatus (Arachnida, Amblypygi) |
|
Authors
|
Institution
|
| Kasey
Fowler-Finn |
Cornell
University |
|
Eileen
Hebets
|
|
|
Abstract:
Whip spiders (Order Amblypygi) comprise one of the
smaller arachnid orders about which surprisingly little is
known. While male-male contests are described as being prevalent
among different amblypygid species (Weygoldt 2001), only basic
descriptions exist and quantitative behavioral studies are
lacking. This study aims to characterize male-male interactions
and to evaluate determinants of contest outcomes in Phrynus
marginemaculatus, a species found in the Florida Keys.
Male contests of this species are characterized by several
behaviors involving some variant of palpal opening (e.g. double
palp opening and asymmetric palp opening), contact with the
antenniform leg by one contestant on different body parts
of his opponent (e.g. contact on the cephalothorax, the legs,
the palps, and the posterior of the prosoma), and extremely
rapid antenniform leg flicking, which is also directed at
a particular location on the opponent’s body (e.g. the
abdomen and the palps). In order to evaluate determinants
of contest outcomes, two pairing treatments were established:
similarly sized males and differently sized males. Contests
were recorded in the dark and preliminary analyses suggest
that weight is a better predictor of who wins than size (as
measured by cephalothorax length and width). The number of
antenniform leg flicks by an individual during a contest also
seems to be correlated with winning. (Added 6 / 18 /
2003)
|
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| Dances
With Wolves Down Under |
|
Authors
|
Institutions
|
| V.
W. Framenau |
Department of Terrestrial Invertebrates,
Western Australian Museum, Perth |
| M.
S. Harvey |
|
A.
D. Austin
|
Centre
for Evolutionary Biology and Biodiversity, The University
of Adelaide, North Terrace, Adelaide, SA, Australia |
|
|
Abstract:
Australia is one of the ‘megadiverse’ countries
of the world and features some of the most unusual animals
and plants. Recent molecular and morphological studies into
the systematics of wolf spiders (Lycosidae) have confirmed
the uniqueness of the Australasian fauna with the re-establishment
of genera that are apparently restricted to Australasia and
the Indo-Pacific, such as Allotrochosina, Venatrix and
Artoria. These studies also revealed challenging problems
in fitting some of these genera into existing subfamilial
categories. This presentation provides an overview of the
history of Australian wolf spider systematics characterized
by the desperate attempts of early European arachnologists
to fit Australian Lycosidae into Northern Hemisphere genera,
which were primarily established with non-genitalic characters.
We give a brief overview of the currently recognized 144 (of
an estimated 500) species currently placed mainly in Lycosa
and Trochosa, and show where they really belong (who
knows, e.g. Dingosa, Tasmanicosa and Hoggicosa?). Australian
wolf spider genera show clear affinities with certain biogeographic
regions, e.g. the dry interior (Hoggicosa, Venator),
or the temperate south-eastern forests of the Dividing Range
(Artoria, Venatrix) which may provide some clues into
the evolutionary radiations of these taxa.
(Added 5 / 23 / 2003)
|
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| A
New Approach To Chemostimulation Of Scorpion Peg Sensilla
Reveals High Resolution Response Properties To Near-Range
Chemostimulants |
|
Authors
|
Institution
|
| Douglas
D. Gaffin |
Department
of Zoology, University of Oklahoma, Norman |
|
Mujahid
A. Hines
|
|
|
Abstract:
Scorpion pectines possess ordered two-dimensional
arrays of thousands of microscopic pegs, each innervated by
about 10 sensory neurons. Previous electrophysiological studies
demonstrated chemosensitivity of peg neurons to volatile organic
compounds blown across the peg fields. We report here a new,
more natural approach for assaying peg chemosensory responses.
Peg sensilla on pectines of Paruroctonus utahensis
were recorded extracellularly with tungsten microelectrodes.
We devised a new method for stimulant delivery, using pure
organic stimulants delivered via glass pipettes with tip diameters
of approximately 10 microns. We used a piezoelectric-driven
micromanipulator to vary the distance between the pipette
tip and the recorded peg sensillum. Stimulant diffusion results
in stronger, more vigorous, and more reproducible responses
than when chemicals are applied in a directed stream (or "puff").
Furthermore, the peg neurons become more responsive with prolonged
stimulation, and spike frequency is inversely related to the
vertical distance between the pipette and the peg. This acute
sensitivity to stimulant distance suggests the ability to
localize point stimuli at the scale of the peg field. We are
currently investigating whether the change in neural activity
of peg sensilla with prolonged stimulation is attributable
to circuit dynamics or altered neural activity in individual
neurons.(Added 6 / 15 / 2003)
|
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| The
influence of chemical vs. visual cues from females on
male courtship behavior in a wolf spider (Araneae: Lycosidae) |
|
Authors
|
Institutions
|
| Jeremy
S. Gibson |
University
of Cincinnati
Department of Biological Sciences |
|
George
Uetz (advisor)
|
|
|
Abstract:
Mate choice by females is usually based on some aspect
of male signaling, but male courtship behavior may not be
independent of the presence of the female. Males of the wolf
spider Schizocosa ocreata use multimodal communication
(visual and vibratory signals) and typically begin courtship
behavior when they encounter the silk of adult females. While
silk alone may be sufficient to elicit a response, it is unknown
whether males use other stimuli from females to initiate courtship.
Moreover, does having more than one stimulus (e.g., visual
contact with the female) increase male courtship vigor? To
test this, males were separated into three female stimulus
treatment groups: visual cues only (female isolated on separate
substrate), chemical (silk) cues only, and chemical (silk)
plus visual cues. Several aspects of male courtship behavior
(chemo-exploratory behavior, jerky-tapping) varied significantly
between treatment groups. Males that were exposed to female
silk performed chemo-exploratory and jerky-tapping behaviors
more often than males given only visual stimuli. Furthermore,
males in the visual treatment group spent more time stationary
than those males in either of the other treatment groups.
These results suggest that male wolf spiders rely more on
chemical stimuli than visual stimuli from females to initiate
courtship behavior. (Submitted 6 / 14 / 2003)
|
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| Spiders
in Fairy Tales of the People in Northern Russia |
|
Authors
|
Institutions
|
| Y.
V. Gorbunova |
Northern
International University, Magadan, Russia |
|
O.P.
Bartosh
|
International
Scientific Center "Arktika", Magadan, Russia |
|
|
Abstract:
Spiders are necessary heroes of fairy tales in every people.
The purpose of our research was to study the spider’s
image in the fairy tales of the aboriginal people, Chukchi,
Asian Eskimos, and Coryaki, in the Northeast of Russia. A
total of 500 fairy tales have been studied. The spider participates
in only 9 of these fairy tales. Four fairy tales of the Asian
Eskimos, three Chukchi’s and one Coryaki’s were
analyzed.
In the four fairy
tales of the Asian Eskimo, the spider in allocated with wisdom
and always helps the heroes of fairy tales that are in a trouble.
In one fairy tale the spider is lowered on a web to the face
of a woman, gives her advice and thus rescues her from the
malicious intention of her husband. One Chukchi’s fairy
tale has a very similar plot involving the rescue of a woman.
In one of the Eskimo fairy tales the spider gives kind advice
and rescues the hero from malicious forces. The spider’s
advice helps the old man to cure an ill reindeer breeder.
In Chukchi and
Coryaki fairy tales the spider carries out the same role of
the helper. In one Chukchi’s fairy tale a spider rescues
a man from the dearth. In Coryaki’s fairy tale the spider
helps a man to get out from underground, where he is doomed
to a hungry death. The spider has a negative character, in
only one Chukchi fairy tale. In this fairy tale he places
the network and catches their people for them. This fantastic
character of the aboriginal peoples of Chukotka and Kamchatka
acts antagonist of the carrier of a malicious beginning -
bug (Bogoraz, 1990).
Thus, in the fairy
tales of the native peoples of the North, the spider is like
the whale killer, raven, wolf, fox, mouse, and loon and plays
the role of the totem helper to man. The spider in the mythology
of the aboriginal peoples of Chukotka and Kamchatka is allocated
with wisdom and helps the heroes who are suffering disaster.
.(Added 5 / 23 / 2003)
|
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| Aversion
Learning In Wolf Spiders: The Persistence Of Memory And
The Role Of Sensory Cues |
|
Authors
|
Institution
|
| Casey
M. Harris |
University
of Cincinnati, Cincinnati OH |
|
George
W. Uetz
|
|
|
Abstract:
We studied the ability of wolf spiders (Schizocosa
ocreata) to recognize and avoid toxic prey after experience.
Milkweed bugs (Oncopeltus fasciatus), were used as
prey in aversion learning experiments. Spiders were assigned
to one of three feeding treatments: 1) toxic (milkweed-fed)
milkweed bugs; 2) toxic cardenolide-free (sunflower-fed) milkweed
bugs; and 3) crickets (Acheta domestica). Spiders were
offered toxic prey until avoidance was exhibited, then offered
alternative prey. Feeding behavior varied with prey type;
spiders accepted crickets and sunflower-fed milkweed bugs,
but rejected toxic milkweed bugs. Spiders acquired aversion
in 1-4 trials and refused cardenolide-free milkweed bugs thereafter,
but accepted crickets. Additional aversion learning experiments
examined the duration of a spider’s learned aversion
to toxic prey and the specific sensory cues (chemical, visual,
tactile) involved in recognition and subsequent avoidance
of potentially toxic prey. Spiders were trained, then re-tested
each day for 4 days and again at 10 days. The mean number
of trials needed to re-acquire aversion decreased by day 3,
and frequency of spiders avoiding milkweed bugs increased
to 100%. This pattern reversed on days 4 and 10, apparently
due to hunger. Studies with video playback and painted milkweed
bugs eliminated visual cues as recognition criteria, but tactile
and chemical cues from O. fasciatus were significant
factors in recognition and avoidance learning. Results suggest
spiders can learn to recognize and avoid distasteful prey,
which may be adaptive for generalist predators. (Added
6 / 12 / 2003)
|
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| The
Potential Role Of Olfaction In Navigation And Mate Finding
In The Amblypygid Phrynus parvulus from Costa Rica |
|
Authors
|
Institutions
|
| Eileen
A. Hebets |
Department
of Neurobiology and Behavior, Cornell University |
|
|
Abstract:
Previous work on the amblypygid Phrynus parvulus
from the tropical forests of Costa Rica found that mate finding
in this species likely consists of males traveling throughout
the environment in search of females, who likely remain stationary
once they find a good crevice. The distances traveled by individuals
are relatively large and the movement patterns suggested that
males may have home ranges that encompass multiple large buttressing
trees. In this heterogeneous tropical environment, the question
remains as to how individuals are navigating throughout the
environment and how they are ultimately locating members of
the opposite sex. In a series of both laboratory and field
experiments, I investigated the potential role of olfactory
cues in both mate finding and navigation. I found that males
seem to be attracted to females with recently dropped eggs
as well as to conspecific males by odor alone and tend to
be deterred by the odor of females carrying eggs. Navigation
studies revealed that individuals are able to navigate their
way home from relatively far distances and results suggest
that odor may play an important role in their navigational
abilities. (Added 6 / 15 / 2003)
|
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| Molecular
Phylogenetics of the Mygalomorph Genus Aliatypus
(Araneae: Antrodiaetidae) |
|
Authors
|
Institutions
|
| Marshal
Hedin |
Department
of Biology, San Diego State University, San Diego, CA. |
| Jason
Bond |
Department
of Biology, East Carolina University, Greenville NC |
|
|
Abstract:
The trapdoor genus Aliatypus includes 11 described
species, basically all endemic to California (a single species
is distributed in Arizona). The genus was revised by Coyle
(1974), with subsequent work by Coyle (1994) and Coyle &
Icenogle (1994), on phylogeny and natural history, respectively.
The genus shows interesting distributional patterns in California
(some taxa are found of both sides of the Sacramento Valley),
is species-rich over a relatively small geographic area, and
occupies an impressive variety of habitats. Some broadly-distributed
taxa display considerable morphological variation over their
ranges. A full understanding this biogeographic, morphological,
and ecological variation requires a solid phylogenetic foundation.
The initial blocks of this foundation were provided by Coyle
(1994), who forwarded a morphology-based phylogenetic hypothesis
for Aliatypus. Here we use DNA sequences from two nuclear
gene regions (18S and 28S) to test the species-level phylogenetic
hypothesis of Coyle (1994), while simultaneously considering
intraspecific phylogenetic divergence of widespread taxa (i.e.,
testing species hypotheses themselves). Many of the broad-scale
phylogenetic patterns suggested by Coyle (1994) are corroborated,
including a general "3 clade" structure for the
genus (A. gulosus, A. californicus group, A. erebus
group). Interestingly, the DNA-based phylogenetic placement
of A. thompsoni is somewhat ambiguous, as also suggested
by morphology. Species with restricted geographic distributions
are, for the most part, monophyletic on gene trees. However,
more widespread taxa are often not monophyletic on gene trees,
perhaps revealing hidden species diversity. Phylogenetically
unique samples from previously unsampled geographic regions
(e.g., south Coastal Ranges) might represent additional novel
species-level diversity. (Added 5 / 8 / 2003)
|
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| Reassessing
The Scorpiofauna Of Saudi Arabia |
|
Authors
|
Institutions
|
| Brent
E. Hendrixson |
East
Carolina University, Department of Biology, Greenville,
NC |
|
W.
David Sissom
|
West
Texas A&M University, Department of Life, Earth &
Environmental Sciences,Canyon, TX |
|
|
Abstract:
This poster briefly discusses the systematics, taxonomy
and species composition of the scorpion fauna of Saudi Arabia.
Examination of several hundred specimens (from the American
Museum of Natural History, British Museum of Natural History,
Field Museum of Natural History, Hebrew University, Museum
of Comparative Zoology, Museum National d’Histoire Naturelle,
Naturhistorisches Museum Basel, and the personal collections
of Matt E. Braunwalder and W. David Sissom) revealed a total
of 13 genera and more than 20 species. Six putatively undescribed
species are identified in the following genera: Buthacus,
Butheolus, Compsobuthus and Hemiscorpius. One new
synonymy is proposed: Vachoniolus minipectinatus is
considered a junior synonym of Vachoniolus globimanus.
Three species are reported from Saudi Arabia for the first
time: Butheolus anthracinus, Compsobuthus longipalpis
and Leiurus jordanensis. Each genus is diagnosed, and
most are accompanied with illustrations and color digital
images; maps have been provided to determine species distributions.
The status of Leiurus quinquestriatus hebraeus is revisited.
Several genera remain problematic and are in need of major
revision because most characters have been found to be as
variable intraspecifically as interspecifically. Finally,
the biogeography of the scorpions of Saudi Arabia is briefly
discussed. (Added 6 / 6 / 2003)
|
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| Web
Spider Diversity in the Riparian forests of SW Ohio |
|
Authors
|
Institutions
|
| T.
Sean Higgins |
Miami
University, Ohio |
|
Christopher
M. Buddle
|
| Ann
L. Rypstra |
|
|
Abstract:
Corridors of riparian forests are often the primary source
of forest habitat in agricultural landscapes. Studies have
shown riparian forest corridors support high terrestrial vertebrate
diversity but few studies have explored their importance to
terrestrial arthropod diversity. We assessed the web spider
diversity in riparian forests in SW Ohio using fixed plot
visual searches. Samples were taken at the stream edge, in
the center, and at the agricultural edge of riparian forests
in three width classes (thin: 15-30 m, medium: 45-60 m, &
wide: >80m from streamside) and the center and agricultural
edge of hedgerows comparable in width to the thin riparian
forests. Species richness and diversity were compared among
forest types using rarefaction and ANOVA. Split – plot
ANOVA allowed comparisons among the edge and center quadrats.
Detrended Correspondence Analysis was used to compare the
species assemblages among sites. Web spiders were significantly
more abundant and diverse in riparian forests than in hedgerows
of similar width. Interestingly, thin riparian forests were
more diverse than wide forests, which, in turn, were more
diverse than medium corridors. Stream edges had the lowest
diversity. The DCA revealed the stream edge community to be
distinct from assemblages in other quadrats. These results
suggest the stream habitat plays a key role in structuring
the adjacent terrestrial spider community, and riparian forest
corridors are important to regional spider diversity in agricultural
landscapes. (Added 6 / 12 / 2003)
|
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| The
Role Of The Web In Prey Capture By Three Species Of Web-Building
Wolf Spiders (Araneae: Lycosidae) |
|
Authors
|
Institution
|
| Maggie
Hodge |
Hiram
College, Hiram, OH |
| Vanessa
Gorley |
|
|
Abstract:
Sosippus is the only genus of wolf spiders (Lycosidae)
in North America that construct prey-capture webs; other genera
are cursorial hunters. The function of a spider web is to
enhance the ability of the spider to capture and subdue prey,
so we hypothesized that Sosippus would capture prey
more quickly with a web than without a web. Sosippus californicus,
S. floridanus, and S. placidus were presented with
live crickets in two conditions: with or without a web. The
time (latency) to subdue the prey was recorded for each condition.
We found that S. placidus and S. californicus
captured prey quicker with webs than without webs (Paired,
1-tailed t-tests, S. placidus: d.f. = 50, t = -2.032,
p <0.05; S. californicus: d.f. = 13, t = 3.408,
p < 0.05). There was no difference in latency to prey capture
with or without a web by S. floridanus (d.f. = 40,
t = 0.848, p = 0.2008). We speculate that since S. placidus
and S. californicus live in xeric habitats, they may
have come to rely on the web to a greater extent than does
S. floridanus, which lives in more mesic habitats.
This may explain why these two species don’t capture
prey without webs as quickly as do S. floridanus (mean
(+ s.e.) time (minutes, seconds) to capture without webs:
S. placidus: 4.34 + 1.38; S. californicus: 8.25
+ 1.26; S. floridanus: 0.47 + 0.31). (Added 6
/ 12 / 2003)
|
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| A
Comparison Of The Diversity Of Ground-Dwelling Spiders
In An Old-Growth Beech-Maple And A Second-Growth Forest |
|
Authors
|
Institution
|
| Maggie
Hodge |
Hiram
College, Hiram, OH |
| Melissa
Varrecchia |
|
|
Abstract:
Beech-maple forests were once widespread throughout Ohio and
Indiana, but uncut, old growth stands are now restricted to
a few small remnant sites. Ground-dwelling spiders are an
important trophic link between the decomposition food web
and the other forest fauna. Their diversity is linked to the
complexity of the leaf litter and prey abundance, both of
which may be greater in later stages of succession (Uetz 1990).
Our ongoing study is designed to measure and compare the diversity
and turnover of leaf litter spiders in a pristine 200-acre
beech-maple forest (100+ years old) and an adjacent, contiguous
second growth forest (<50 years old) in northeast Ohio.
Eight pairs of pitfall traps were sampled in each habitat
at weekly intervals from July-September, 2001 & 2002.
We compared the familial and generic diversity in the two
habitats, and changes in diversity and abundance from year-to-year.
The most abundant genera in both habitats were Wadotes
(Amaurobiidae) and Neoantistea (Hahniidae). Wadotes
was over twice as abundant in second-growth traps in 2001,however
this difference vanished in 2002. Neoantistea is similarly
abundant in both habitats, but increased dramatically (almost
7 fold) in 2002. In both years Agroeca (Liocranidae)
was more abundant in the second-growth, whereas Phrurotimpus
(Liocranidae) and Pirata (Lycosidae) where more abundant in
the old-growth. Contrary to expectation, there were no differences
in diversity between the habitats. The number of genera captured
in each habitat was greater on most dates in the second-growth
sites but this difference was not significant. (Added
6 / 12 / 2003)
|
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| Two
New Species of Sabacon Harvestmen, with Descriptions
of the Females of Sabacon astoriensis Shear and
Sabacon sheari Cokendolpher, from Western North
America (Arachnida, Opiliones, Sabaconidae) |
|
Authors
|
Institutions
|
| Robert
G. Holmberg |
Centre
for Science, Athabasca University, Athabasca, Alberta |
| Donald
J. Buckle |
620
Albert Street, Saskatoon, Saskatchewan |
|
|
Abstract:
Two new species of Sabaconidae (Ischyropsalidoidea)
are described: Sabacon # 1 from central Alberta and
British Columbia and Sabacon # 2 from Oregon. Descriptions
of the females of Sabacon astoriensis Shear 1975, from
Oregon, and Sabacon sheari Cokendolpher 1984, from
Oregon and Idaho, are also described.(Added 5 / 23 /
2003)
|
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| Immunoreactivity
of Glutamic Acid Decarboxylase (GAD) Isoforms in the Central
Nervous System of the Barn Spider, Araneus cavaticus |
|
Authors
|
Institutions
|
|
Hee-Jun Hwang |
Department
of Biological Sciences, Dankook University, Cheonan 330-714,
Korea |
|
Edward
K. Tillinghast
|
Department
of Zoology, University of New Hampshire, Durham NH, USA |
| Myung-Jin
Moon |
Department
of Biological Sciences, Dankook University, Cheonan 330-714,
Korea |
|
|
Abstract:
The g-aminobutyric acid (GABA) has long been considered
an inhibitory neurotransmitter in the central nervous system
(CNS) of both vertebrates and arthropods. The glutamic acid
decarboxylase (GAD) catalyzes the conversion of L-glutamate
to GABA. As the GAD has a restricted tissue distribution,
it is highly expressed in the cytoplasm of GABAergic neurons
in the CNS. However it is also present in other non-neuronal
tissues such as testis, oviduct and ovary. Recently, there
were reports that a GABA-like immunocytochemical reactivity
and a ninhydrin-positive GABA derivative, GABamide, exists
in the visual ganglia and in the water-soluble fraction of
the spider web respectively. So, this experiment initiated
to identify exact distribution of the GAD isoform immunoreactivity
in the CNS of the spider to reveal the ecophysiological significance
of GABA for spider's behavior. (Added 6 / 17 / 2003)
|
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| Dynamics
of Group Formation in Pholcids: Lessons from a Long-Term
Study |
|
Author
|
Institution
|
|
Elizabeth
M. Jakob
|
Dept.
of Psychology, University of Massachusetts,
Amherst |
|
|
Abstract:
I will integrate results from my long-term study of facultative
group living in Holocnemus pluchei (Family Pholcidae).
I was especially interested in how individual variation impacts
group dynamics, a problem that is more tractable in H.
pluchei than in many other taxa. In a series of laboratory
and field experiments, I documented that individual variation
in size, sex, and recent feeding success all influence spider
behavior, sometimes in surprising ways. I will discuss briefly
current popular methods of modeling the role of individual
variation in social groups and why some are less appropriate
for spiders, and describe the value of a spatially explicit,
object-oriented approach.(Added 6 / 12 / 2003)
|
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| Territory
Size And Spacing Patterns In The Wolf Spider, Pardosa
milvina (Araneae; Lycosidae) |
|
Authors
|
Institution
|
| Kimberly
Jansen |
Miami
University, Ohio |
|
Ann
Rypstra
|
|
|
Abstract:
In active spider species, the number of encounters
they have with conspecifics can have important consequences
to both reproduction and survival. In a simple laboratory
experiment, we explored the factors that influence spacing
and aggression levels between females of the active wolf spider,
Pardosa milvina (Araneae; Lycosidae). In each trial, two
females were placed in arena and the distance between them
and any interactions were monitored for 15 minutes. In different
treatments we explored whether their behavior was affected
by body size differences, and/or habitat quality (moisture,
presence of prey or predator information). Spiders that were
similar in size moved closer together than those that were
asymmetrical in size. Presumably they could tolerate one another
better because the threat of cannibalism was lower. Spiders
in a moist environment were found closer together and attacked
one another more than those on a dry substrate. Spiders held
in the presence of cues left by crickets (the prey items they
had been maintained on most recently) moved closer together
and came in contact with one another more than spiders held
on conspecific cues or on cues from a common predator, Hogna
helluo (Araneae; Lycosidae). Thus spiders in high quality
environments (moisture and/or prey present) tended to interact
more than those in a hostile environment (dry and/or risk
of predation). We presume these increased interaction levels
are due to a higher activity level under good conditions.
(Added 6 / 18 / 2003)
|
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| Los
Angeles Spider Survey Completes Its First Year |
|
Authors
|
Institution
|
| Janet
Kempf |
Natural
History Museum of Los Angeles County |
|
Vygandas
Relys
|
|
|
Abstract:
For the past year, the Natural History Museum of Los
Angeles County has conducted an urban spider survey of the
greater Los Angeles area. The public was invited to participate
by collecting spiders in their houses and gardens, recording
collection data, and bringing them to the museum. Approximately
2500 spiders have been collected by the public and by museum
arachnologists. Most of the spiders were collected from houses
and gardens in urban areas of Los Angeles County. Approximately
35% of the spiders collected were in the family Theridiidae.
Steatoda grossa (Theridiidae) was the most common spider
at 20% of all specimens received, and was found both inside
and outside. The most commonly found spiders indoors included:
Cheiracanthium mildei (Miturgidae), 7%; Scotophaeus
blackwalli (Gnaphosidae), 8%; Oecobius navus (Oecobiidae),
6%; and Pholcidae, 19%. The most common spiders found outside
were: Agelenidae (predominantly Hololena curta), 16%;
various Araneidae, 9%; Latrodectus hesperus ( Theridiidae),
8%; and Achaearanea tepidariorum (Theridiidae), 7%. ). The
majority of the most common species found in the LA area were
typical cosmopolitan species; Cheiracanthium mildei,
Latrodectus hesperus, and most of Agelenidae and Araneidae
can be considered as a true native species adapted to an urbanized
environment. Three species collected appear to be new records
for the area: Latrodectus geometricus (Theridiidae);
and Tylogonus minutus and Plexippus paykulli (Salticidae.
The Los Angeles Spider Survey will continue with an emphasis
on collecting in natural areas within the Los Angeles area.
(Added 6 / 18 / 2003)
|
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| A
Study of the Eocene Spiders from Florissant, Colorado |
|
Authors
|
Institutions
|
| April
Kinchloe |
University
of Colorado Department of Geological Sciences, Boulder |
|
Paula
Cushing
|
Denver
Museum of Nature and Science Department of Zoology Denver,
CO |
|
|
Abstract:
The 34.1 million year old Florissant formation in
central Colorado holds some of the most beautifully preserved
and unique fossils from the Tertiary. This well known deposit
is rich with fossil plants, vertebrates, and arthropods, which
have been studied for over one hundred years. The order Araneae,
is among the most diverse groups on earth and is abundant
within the Florissant formation. It is believed that this
order originated in the Devonian, with a major radiation in
the early Mesozoic. Many of the modern families have origins
well into the Late Cretaceous. Generally, fossil deposits
containing spiders are rare, however, the record from the
Tertiary is robust based on amber deposits in Europe and the
Dominican Republic and fossil shale deposits like Florissant.
As a result, Florissant is internationally renowned for its
rare and excellently preserved spider fossils. Two previous
researchers, Samuel Scudder in the late nineteenth century
and Alexander Petrunkevitch in the early twentieth century,
had researched the Florissant spider assemblage. Both identified
these specimens to the species level. When looking at modern
spiders, many generic and all specific designations are based
on genitalic characters. Although the fossils are exquisitely
preserved, this important character is not clearly visible
in any of the specimens. As a result, it is my intention to
re-evaluate the placement of these fossils. (Added 6
/ 16 / 2003)
|
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| The
Effects of Mating and Sperm Storage on the Behavior of
Female Fishing Spiders |
|
Authors
|
Institution
|
| Nancy
Kreiter |
College
of Notre Dame of Maryland, Baltimore, Maryland |
|
Amber
Ehlman
|
|
|
Abstract:
Male accessory gland secretions passed to females
during copulation may reduce female receptivity in some insects.
Manipulative effects of seminal products are not reported
in spiders, but decreased or loss of sexual receptivity of
females after a single mating occurs in several species. Female
Dolomedes triton rarely re-mate, and previously-mated
females often cannibalize courting males. We tested the hypothesis
that this reduced receptivity and increased aggression is
a induced through seminal fluid. Virgin female D. triton
were mated with males that were unable to complete sperm induction;
the male genital pore was sealed with paraffin shortly after
molting. Control groups were either mated with normal males
or had no prior mating experience. Behavioral comparisons
were made between groups during trials with normal, intact
males at two time points: 24 hours after initial mating and
14 days later. Previous mating experience, whether sperm was
transferred or not, resulted in a loss of receptivity. However,
sperm storage was associated with attacks of males by females.
Males paired with females that were storing sperm produced
fewer courtship behaviors. Reduced receptivity in females
appears to be controlled by palpal insertion during mating,
while increased aggression towards males and the elicitation
of courtship behavior from males appear to be controlled by
the presence of sperm. (Added 6 / 16 / 2003)
|
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| The
Effect of Nutritional Limitation and Chemical Cues on
the Foraging Behavior of the Wolf Spider Pardosa milvina
(Araneae, Lycosidae) |
|
Authors
|
Institutions
|
| Marlena
Koper |
Department
of Zoology, Miami University, Oxford, OH |
|
Ann
L. Rypstra
|
| Matthew
H. Persons |
Department
of Biology, Susquehanna University, Selinsgrove, PA |
|
|
Abstract:
Theory suggests that foraging behavior is shaped by the trade-offs
made by animals under selection pressure to maximize their
fitness. A potential trade-off exists between balancing hunger
and exhibiting anti-predator behaviors which may detract from
foraging. Although anti-predator behaviors (e.g. avoidance
and vigilance) are well documented in the small wolf spider
Pardosa milvina (Araneae: Lycosidae), little is known
about how energetically stressed organisms balance conflicting
information regarding the presence of predators and prey.
Since P. milvina is known to respond to chemical cues
left by other organisms in its environment, we were able to
manipulate food-limited individuals using cues from predators,
prey, or both. Under these various conditions, we monitored
the overall activity level and foraging behavior of female
P. milvina. Contrary to previous findings, well fed
and food limited spiders differed significantly in their behavior.
In general, food limited spiders were more active and had
a greater propensity to forage than well fed spiders. Additionally,
food restricted spiders demonstrated a stronger response to
different environmental cues when compared to those that were
well fed. The results of this study contribute to our understanding
of the trade-offs made by Pardosa when managing the
competing risks of starvation and predation. (Added
6 / 12 / 2003)
|
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| The
Phylogeny of the Oarcinae (Araneae, Mimetidae) |
|
Authors
|
Institution
|
| Stephen
E. Lew |
University
of California, Berkeley |
|
Rosemary
G. Gillespie
|
|
|
Abstract:
The Mimetidae are a spider family of worldwide distribution
and problematic taxonomic placement. The Oarcinae are a subfamily
of mimetid spiders endemic to temperate Chile and adjacent
Argentina. Their evolutionary history is of particular interest
because of the Chilean biogeographic province’s unique
role in planetary diversity. Moreover, their close resemblance
to orbicularians is relevant to certain controversies regarding
the inter-familial placement of the Mimetidae. There are seven
oarcine species, placed in the monotypic genus Oarces
Simon and the slightly larger genus Gnolus Simon. All
seven are recently revised and well delimited. The taxa are
scored for morphological characters and a phylogeny is inferred
under parsimony. The analysis strongly supports the monophyly
of the Oarcinae with respect to other mimetid spiders, but
does not support monophyly for either oarcine genus. Photographic
evidence of araneophagy in oarcines, and a literature review
of mimetid taxonomy are also presented. (Added 6 / 17
/ 2003)
|
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| Salticid
Molecular Phylogenetics |
|
Authors
|
Institutions
|
| Wayne
Maddison |
University
of British Columbia, Vancouver, British Columbia |
| Marshal
Hedin |
San
Diego State University, San Diego, California |
|
|
Abstract:
We review progress to date in resolving salticid phylogeny
using molecular data. Data from our sample of 81 genera sequenced
for 5 genes corroborate some previously recognized groups
(e.g., dendryphantines, plexippines) and strongly support
some novel groupings (pellenines+plexippines; dendryphantines+marpissines;
sitticines+amycines+others). Additional sampling of Old World
groups is needed to resolve the placement of groups such as
Salticus, Neon and Myrmarachne, whether
aelurillines and freyines are closely related, and other puzzles.
We hope that the clarification provided by molecular data
will help us notice morphological synapomorphies (e.g., tegular
ledge, leg structure?), which could provide the next round
of resolution of the family's phylogeny. Our current phylogeny
offers insight into chromsome evolution (amycoids and pellenines
with unusually high rates of change) palp evolution (polyphyly
of free-embolus salticids), and biogeography (deep division
of Old and New World). Molecular data are also resolving relationships
among closely related species, but not without difficulties.
Our data from Habronattus have resolved various clades,
but hybridization in some species groups may be obscuring,
or even corrupting, a simple branching phylogeny. (Added
6 / 21 / 2003)
|
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| A
Survey Of Baltic Amber Theridiidae (Araneae) Inclusions
With Descriptions Of Six New Species |
|
Authors
|
Institutions
|
| Yuri
M. Marusik |
Institute
for Biological Problems of the North, Portovaya Str. 18,
Magadan, 685000 Russia email:
yurmar@mail.ru |
| David
Penney |
Earth
Sciences, The University of Manchester, Manchester, M13
9PL, UK email:
david.penney@man.ac.uk |
|
|
Abstract:
Baltic amber spider inclusions previously placed in the family
Theridiidae are reviewed. Six new species from the Palanga
Amber Museum collection are described: Episinus (two
species), "Euryopis" (one species) and Nanomysmena
(three species). Nanomysmena Petrunkevitch, 1958 is
removed from synonymy with Clya Koch & Berendt,
1854. Four new combinations are established: Episinus kaestneri
(Petrunkevitch, 1958) comb.n. ex. Eodipoena Petrunkevitch,
1942, Episinus longimana (Koch & Berendt, 1854)
comb.n. and Episinus succini (Petrunkevitch, 1942)
comb.n. both ex. Flegia Koch & Berendt, 1854, "Steatoda"
stigmatosa (Koch & Berendt, 1854) comb.n. ex.
Teutana. Forty-one theridiid species from Baltic amber
are currently attributed to 14 genera. The most species rich
genera are Nanomysmena Petrunkevitch, 1958 (six species),
Eodipoena Petrunkevitch, 1942 and Episinus Walckenaer,
1809 (each with five species). However, eight fossil species
are attributed to Theridion Walckenaer, 1805 but it
seems that they were incorrectly placed in this genus and
no diagnostic illustrations were provided in the original
descriptions. The correct placement of several fossil species
originally attributed to the genera Eodipoena, Episinus
and Steatoda is also questionable. Judging from the
structure of the copulatory organs and somatic morphology
it seems that many fossil Theridiidae species are incorrectly
placed. Recent and fossil Episinus require revision.
As Theridiinae inclusions are absent from the Baltic amber
fauna, the age of this subfamily is probably younger than
mid-Eocene.(Added 4 / 25 / 2003)
|
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| Foraging
and Habitat Selection by the Scorpion, Centruroides
vittatus |
|
Author
|
Institution
|
| C.
Neal McReynolds |
Texas
A&M International University, Laredo, Texas |
|
|
Abstract:
How does habitat selection effect the foraging success of
the scorpion, Centruroides vittatus (Scorpiones: Buthidae)?
The frequency of prey capture by C. vittatus was observed
on the campus of Texas A&M International University in
the Tamaulipan Biotic Province. The frequency of prey capture
was significantly different for microhabitat classes. Prey
capture frequency was higher for scorpions on blackbrush,
Acacia rigidula, than other microhabitats and low when
on the ground or cacti. Prey capture frequency was significantly
higher with increased height on foliage. Prey capture frequency
was significantly higher during March through May and September
through October but not significantly different among temperature
or humidity classes. Caterpillars of Lepidoptera were an important
prey item (15 caterpillars of 45 prey items), and most of
the captured caterpillars were observed on blackbrush (9 of
15). Why was foraging success of a C. vittatus higher
in blackbrush? Further research will investigate prey availability
on different plant species and at different seasons to compare
with foraging success of scorpions. Why were scorpions located
in microhabitats with low foraging success? Further research
on the home range of C. vittatus will investigate uses
of microhabitats (i. e., foraging or as refuges). (Added
6 / 18 / 2003)
|
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| Evaluating
Species Richness Of Wandering Spiders In A Mangrove Forest
Of Chiapas, Mexico |
| Author:
Francisco Medina |
|
Institution:
Laboratorio de Acarología "Anita Hoffmann".
Facultad de Ciencias, UNAM. México
|
|
|
Abstract:
Wandering spiders comprise a minor proportion of the spider
fauna in the mangrove forest of "La Encrucijada",
Chiapas. From collections carried out during the wet season
2002 and the dry season 2003, only 31 species were identified,
while more than eighty were obtained from the web-spinning
spider collection. This web spiders dominance is thought to
be due to the characteristic vegetation structure of the mangrove.
Four estimators were used to evaluate the expected species
richness: ACE (Abundance Coverage Estimator), Chao1, the first
order Jacknife and the Michaelis-Menten equation. Estimated
species richness was very close to the observed values in
the wet season, except the Michelis-Menten equation. In the
dry season, however, the sample resulted less complete and
estimated richness was higher than observed with every estimator.
Some species which in the dry season appeared in considerable
number, were represented by only one or two individuals in
the dry season, thus elevating the number of singletons and
doubletons and therefore, causing the estimate to be less
compatible with what we observed. Some spiders were found
to have their active adult period separated between seasons,
others were more abundant, and others were exclusive of one
season. The reasons for such distribution in time and some
notes on their microhabitats as seen in the field are discussed.
(Added 6 / 16 / 2003)
|
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The
Unbearable Lightness of Being Monophyletic. Clade Stability
and the Addition of Data — A Case Study from Erigonine
Spiders (Araneae:
Linyphiidae, Erigoninae) |
|
Authors
|
Institutions
|
| Jeremy
A. Miller |
Smithsonian
Institution
and The George Washington University, Washington D.C. |
| Gustavo
Hormiga |
The
George Washington University
and Smithsonian Institution, Washington D.C. |
|
|
Abstract:
We present a new hypothesis of relationships among erigonine
spiders based mainly on morphological characters. We have
added taxa and characters to a previous analysis of erigonine
relationships. Nearly all of the taxa added for the current
analysis represent Neotropical genera. Cladistic analysis
of the expanded matrix results in a single most parsimonious
tree. Our phylogeny differs markedly from the previous cladistic
hypothesis of erigonine relationships. We investigate how
the addition of characters and taxa (alone and together) has
altered the original phylogeny of erigonine genera. We conclude
that topological changes from the previous study to the current
one are largely the result of adding and modifying characters,
not adding taxa. Our phylogeny has implications for hypotheses
of character evolution in erigonines. (Added 4 / 25
/ 2003)
|
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| A
Comparison of the Femoral Gland of Zodarion rubidium
(Araneae, Zodariidae) with that of Other Species of Zodariidae |
|
Authors
|
Institutions
|
| Lourdes
Montoya |
Denver
Museum of Nature & Science |
|
Catherine
Tuell
|
Colorado
School of Mines |
| Paula
E. Cushing |
Denver
Museum of Nature & Science |
|
|
Abstract:
Many of the members of the family Zodariidae possess femoral
glands. The function of these glands is unknown. Our objective
was to use Scanning Electron Microscopy (SEM) to determine
the structure of the femoral gland of Zodarion rubidium,
one of two species of Zodarion found in the United States.
This species was originally documented from Pennsylvania by
Bea Vogel in the 1960’s and was discovered in Colorado
by Colorado Spider Survey participants, Nina Shilodon and
Steven Bonham in 1999. The femoral glands of Z. rubidium
are compared with the glands found in other species in the
family Zodariidae. (Added
5 / 20 / 2003)
|
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| Fine
Structural Analysis of the Central Nervous System in the
Spider, Achaearanea tepidariorum (Theridiidae:
Araneae) |
|
Authors
|
Institutions
|
| Myung-Jin
Moon |
Department
of Biological Sciences, Dankook University, Cheonan 330-714,
Korea |
|
Hee-Jun
Hwang
|
Department
of Biological Sciences, Dankook University, Cheonan 330-714,
Korea |
| Chang-Soo
Kang |
Department
of Life Sciences, Hoseo University, Cheonan 336-795, Korea |
| Sung-Moon
Yoe |
Department
of Biological Sciences, Dankook University, Cheonan 330-714,
Korea |
|
|
Abstract:
The central nervous system (CNS) of spiders has a
lot of area in need of desciption.The CNS of Achaearanea
tepidariorum, consists of a dorsal brain or supraesophageal
ganglion and circumesophageal connectives joining it to the
subesophageal masses. We classify the brain as a protocerebral
and tritocerebral ganglion depending on its body segmentation
and other segmentation features. The subesophageal nerve mass
underneath the brain is the foremost part of the ventral nerve
cord. All of this nerve mass is totally fused together, and
forming subesophageal ganglia in this spider. While the nerve
cells are packed in the frontal, dorsal and lateral areas
of the brain, the nerve cells of the subesophageal and abdominal
ganglia are only restricted to the ventral and ventolateral
regions. It has been revealed that the organization of the
CNS of this spider, Achaearanea tepidariorum is more
similar in feature to the family Araneidae rather than other
web-building spiders.(Added 6 / 18 / 2003)
|
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| Functional
Organization of the Silk Spinning Apparatus in Funnel-web
Spider, Agelena limbata (Araneae: Agelenidae) |
|
Authors
|
Institutions
|
| Myung-Jin
Moon |
Department
of Biological Sciences, Dankook University, Cheonan 330-714,
Korea |
|
Jong-Gu
Park
|
| Sung-Moon
Yoe |
| Chang-Soo
Kang |
Department
of Life Sciences, Hoseo University, Cheonan 336-795, Korea |
|
|
Abstract:
Silk apparatus of the funnel-web spider, Agelena
limbata was located at the ventral end of the abdominal
part, and was composed of internal silk glands and external
spinnerets. Among the three pairs of spinnerets, the posterior
pairs were highly elongated along the body axis. By the light
and electron microscopic inspections, it was found that four
types of silk glands were connected through the typical spinning
tubes of each spinneret. Anterior spinnerets comprise 2 pairs
of the ampullate and 125 to 150 pairs (female) or 110 to 114
(male) of pyriform glands. Another 2 pairs of ampullate glands
in both sexes, 5 to 8 pairs of tubuliform glands in females,
and 20 to 26 pairs (female) or 15 to 17 pairs (male) of aciniform
glands were connected on the median spinnerets. Additional
8 to 10 pairs of tubuliforms in female and 41 to 53 pairs
(female) or 27 to 32 pairs (male) of aciniform glands were
on the posterior spinnerets, respectively. While the ampullate
and tubuliform glands were connected with the spigot-type
spinning tubes, the pyriform and aciniform glands with that
of spool-type tubes. It has been also revealed that the tubuliform
glands were only observed in female spiders, however the flagelliform
and aggregate glands which had the function of adhesive thread
production in orb-web spiders were not observed at both sexes
of this spiders. (Added 6 / 18 / 2003)
|
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| Individual
and Combined Effects of Birds and Ants on Spiders in Ponderosa
Pine Canopies |
|
Author
|
Institution
|
| Kailen
A. Mooney |
University
of Colorado, Dept. EE Biology, Boulder |
|
|
Abstract:
Predator exclusion experiments have shown that both
birds and ants can be important predators of spiders in forest
canopies. Other work has demonstrated that the effects of
multiple predators are often not independent of each other.
To test whether there is interaction between the effects of
these predators I conducted a three-year factorial experiment
of bird and ant exclusion (i.e. bird exclusion, ant exclusion,
dual exclusion and control treatments) in the canopies of
ponderosa pine (Pinus ponderosa var. scopulorum)
at the U.S. Forest Service Manitou Experimental Forest, Colorado,
USA. This experiment has allowed me to identify the individual
and combined effects of canopy foraging birds (Chickadees
[Parus spp.] and Nuthatches [Sitta spp.]) and
the ant Formica podolica on the web spinning and cursorial
spiders in this system. In total I observed 13 species of
cursorial spiders in five families and 14 species of hunting
spiders in five families. Web spinning spiders were negatively
affected by ants (exclusion led to a 30% increase), but not
by birds. Cursorial spiders were negatively affected by both
ants and by birds, and there was a significant interaction
between the two predator effects; Bird exclusion increased
spider abundance by approximately 60% in the absence of ants,
but only by 20% in their presence. These results suggest that
when we characterize individual predators-prey interactions,
the effects we measure may only be meaningful within the context
of the larger predator community within which they are studied.
(Added 6 / 17 / 2003)
|
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| Mechanical
Properties of Major Ampullate Silk from the Brown Widow
Latrodectus geometricus |
|
Authors
|
Institution
|
| Dagmara
Motriuk-Smith |
University
of Wyoming, Laramie, WY |
|
Randolph
V. Lewis
|
|
|
Abstract:
Major ampullate (dragline) silk is the main web component
as well as the silk that spiders use as a lifeline when they
fall. This silk has a breaking stress of 4.6 GPa, which is
similar to that of Kevlar. The majority of the mechanical
testing studies have involved the major ampullate silk from
orb-weaving spiders. To date, there have been no reports on
dragline silk mechanical properties from a brown widow, Latrodectus
geometricus.
L. geometricus dragline is composed of two proteins
MaSp1 and MaSp2, both of which have highly conserved amino
acid motifs, especially the GGX, GA and poly A for MaSp1 and
GPGGX and poly A for MaSp2. These sequences are the same as
those found in the orb-weaving spiders.
To determine if web structure and protein sequences influence
the material properties of the silk, mechanical testing was
performed on single strands of silk fibers from anesthetized
adult female L. geometricus spiders. The 3 cm long
silk fibers were tested for breaking stress and strain with
a MTS Synergie 100 mechanical testing system using a 5 g load
cell with the cross-head speed set at 10 mm/min. The breaking
stress and strain were measured for 20 replicate samples and
averaged. The values of 0.94±0.19 GPa for stress and
0.14±0.06 for strain suggest that brown widow dragline
is one of the weakest ever reported. (Added 6 / 6 /
2003)
|
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| Digital
Imaging Techniques in Arachnology |
|
Author
|
Institution
|
|
Matthew
K Nelson
|
University
of Texas at Arlington |
|
|
Abstract:
The increase in availability of digital imaging devices over
the past decade has resulted in many new and exciting applications
in the field of arachnology. With the help of digital photomicroscopy,
it is now possible to use quantitative methods to analyze
palpal and epigynal morphology in ways which were previously
impossible or extremely difficult. Inexpensive digital scanners
allow the measurement of many morphological features that
were previously only addressable by quantitative techniques.
One of the most useful features of digital imagery is the
ability to measure the 2-dimensional area of an object. It
is also possible to quantify color patterns and shading using
digital techniques. We used digital techniques to measure
palpal variation among populations of a wolf spider. We were
able to reliably measure structures on the palp with minimal
error. We were also able to measure variation in color pattern
on the ventral aspect of the body and legs. These techniques
have broad applicability across many scientific disciplines,
and are particularly useful in arachnology. (Added 6
/ 12 / 2003)
|
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| Population
Structure Of The Spider Waitkera waitakerensis
(Uloboridae): Does It Really Comprise A Monotypic Genus? |
| Author:
Brent
Opell |
|
Institution:
Department
of Biology, Virginia Tech, Blacksburg, VA
|
|
|
Abstract:
The genus Waitkera is the only New Zealand representative
of the family Uloboridae and is known from a single species,
Waitkera waitakerensis (Chamberlain, 1946). This species
is common in forests of the North Island, where it constructs
orb-webs on under story vegetation. Rock outcrops in the Northland
region support populations of W. waitakerensis comprised
of larger individuals than those found elsewhere on the island,
including those in surrounding forests. However, analysis
of DNA sequences of the mitochondrial NADH dehydrogenase subunit
ND1 with parsimony and TCS estimation does not delineate these
rock-dwelling populations as a monophyletic lineage that might
be regarded as a distinct species. Instead, they appear to
represent an ecotype. The low genetic variability of W.
waitakerensis and its population structure suggest that
this species contracted to the Northland during the Pleistocene
and that it then colonized the North Island via the Coromandel
Peninsula.(Added 6 / 6 / 2003)
|
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| Ontogenetic
Changes in the Foraging Behavior of Argyrodes trigonum |
|
Authors
|
Institution
|
| Michelle
Osgood |
Dept.
of Biology, Keene State College, Keene, NH |
|
Karen
Cangialosi
|
|
|
Abstract:
Argyrodes trigonum is a species of spider that utilizes
a range of foraging strategies: kleptoparasitism, host predation,
web stealing and web sharing, as well as constructing its
own web. Previous work has shown that foraging strategy is
influenced by a variety of factors including developmental
stage of A. trigonum. However, differences in foraging
for different instars of spiders may be merely the result
of differences in size of the host spider relative to A.
trigonum. The objective of this study was to elucidate
ontogenetic changes in foraging behavior that result from
factors other than relative host size. The foraging behavior
of all instars (1-6) of A. trigonum in the webs of
the host spider, Achaearanea tepidariorum was observed.
Host size was varied for each instar of A. trigonum.
Spiders were kept in ten-gallon aquaria, containing one host
spider and one A. trigonum. Observations of positions
and interactions between host and A. trigonum were
recorded several times daily for three days. Earlier (1st-3rd)
instar A. trigonum exhibited more aggressive foraging
tactics as well as more active behavior in general regardless
of host size compared to 4th instar A. trigonum. Adult
female A. trigonum also exhibited aggressive behavior.
The more passive behavior of mid-sized individuals could be
due to their need to redirect energy from active foraging
into the final molt to sexual maturation. (Added
6 / 12 / 2003)
|
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| Blind
Cicurina (Araneae: Dictynidae) From Texas Caves:
A Molecular Application For Conservation |
|
Authors
|
Institution
|
| Pierre
Paquin |
San
Diego State University |
|
Marshal
C. Hedin
|
|
|
Abstract:
Many troglobitic species have limited distributions
and deserve conservation status. The genus Cicurina
consists of 128 described species of which º50 are cave obligate
spiders. These species have typical morphological adaptations
of troglobitic organisms such as reduction/loss of pigmentation
and eyes. Blind Cicurina are numerous in Texas and
currently 4 species have been designated as federally protected.
The rarity of these spiders, sampling difficulties, and conservation
status limit the number of specimens available for reliable
species identification. In addition, females exhibit high
intraspecific variation with many species being similar, juveniles
are impossible to identify to species, and males are very
rare (known only for 7 species). The rarity of these spiders,
coupled the with the identification difficulties, is problematic
as species level identification is required to assign conservation
priorities to caves. In this study, we used phylogenetic analyses
of º1000 base pairs of the mtDNA gene CO1 to examine the utility
of molecular data in species identification of troglobitic
Cicurina. The estimation of genetic variability of
adult voucher specimens provides a molecular tool to identify
immatures, often the only material available. Previous studies
and collections have suggested that there are typically two
Cicurina species per cave: One eyeless species (subgenus
Cicurella) and Cicurina varians, a fully-eyed
species (subgenus Cicurusta). Our results support that
only one blind species occurs per cave, and also show that
no hybridization occurs between C. varians as the two
lineages were always recovered. Our results have implications
for conservation biology and also provide insights into the
systematics of the genus and evolution of troglobitic species.(Added
6 / 6 / 2003)
|
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| Ladies
And Tramps: Alternative Reproductive Strategies In Salticidae |
|
Authors
|
Institutions
|
| Frank
H. Pascoe |
University
of St. Francis, Joliet, IL |
| David
L. Clark |
Alma
College, Alma, MI |
|
|
Abstract:
Jackson (1978, 1980, 1981, 1986) has documented agonistic
and cohabitation behaviors of Phidippus johnsoni males.
Males engage in visual and physical contests, even with no
female present. Female Phidippus reproductive anatomy
and sterile male breeding experiments (Jackson 1980) support
the precedence of first male sperm in Phidippus. From
the female’s perspective, the agonistic, cohabitating
male reproductive strategy is an elegant solution to the balance
between female reproductive security and female choice. This
type of reproductive behavior has been observed in several
Phidippus species and a number of other salticid genera.
Jackson and Willey (1995) have suggested that the cohabitation
of males with juvenile females may be a "universal"
reproductive strategy in salticids. However, our field observations
with Maevia inclemens have shown that there is a least
one alternative reproductive strategy used by salticids.
M. inclemens males have no cohabitation or inter-male
agonistic behaviors. Instead the dimorphic males wander through
"lek-like" areas at the interface of woodland/prairie
habitats searching for females. Females have short-duration
(typically less than ten seconds) matings with multiple males.
In addition, the female genitalia of Maevia do not
appear to support the first male precedence model. This alternative
reproductive strategy may be a significant factor in the evolution
of dimorphic males in Maevia inclemens. (Added
6 / 6 / 2003)
|
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| Burrowing
Scorpion Phylogeny And The Evolution Of Palaeodrainage
Systems In Southern Africa |
|
Authors
|
Institutions
|
| Lorenzo
Prendini |
American
Museum of Natural History |
|
Timothy Crowe
|
Percy FitzPatrick Institute, University of Cape Town,
South Africa |
| Ward
Wheeler |
American
Museum of Natural History |
|
|
Abstract:
The Orange River is the largest crossing the arid
interior and western coastline of southern Africa. Geological
evidence suggests that it underwent major drainage system
changes during late Cretaceous-Cainozoic times, including
alternations in use of the 28 degrees S (modern Orange River)
and 31 degrees S (modern Olifants River) exit points and radical
reorganisations of internal drainage geometry. During the
late Cretaceous, the 28 degrees S exit was used, and the middle
Orange River followed a course up to 150 km south of its modern
channel. Two subsequent alterations in exit point occurred
in the late Cretaceous-early Tertiary (31 degrees S) and late
Oligocene-early Miocene (28 degrees S exit). Other internal
reorganisations coincided with palaeoclimatic oscillations
between the late Miocene and Pleistocene, until the present
course was achieved.
The burrowing scorpion (Scorpionidae: Opistophthalmus) faunas
occurring north and south of this river are distinctly different.
Only five species occur on both sides. The remaining 75 are
endemic either to the region north (Namibia) or south (South
Africa). A spatial dataset of ca. 8 000 point locality records
for Opistophthalmus species is used to plot their distributions
in relation to the present and palaeodrainage channels. Areas
of present occurrence are optimized on a cladogram for Opistophthalmus
species, derived from a simultaneous analysis of 262 morphological
characters and 1.8 kilobases of DNA sequence. Not only the
five transriverine distributions, but the evolution of the
largest clade of Opistophthalmus species, are inferred as
consequences of dispersal and vicariance associated with drainage
shifts that coincided with the development of increasingly
arid conditions in southwestern Africa. (Added 5 / 20
/ 2003)
|
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to the top of the page
| Searching
for Competition: Sympatry and Interactions Between Two
Agelenid Spiders |
|
Author
|
Institution
|
| Marius
Pfeiffer |
University
of Texas at Arlington, Fort Worth Texas |
|
|
Abstract:
.Similar predatory species living in close proximity
can be assumed to interact along one or more axes of their
niche space. Typical axes or resources of concern are physical
space, substrate, time and prey. If species are to persist
in sympatry, limiting resources should be partitioned to some
degree. Inter-specific competition can be considered in cases
of unstable overlap of resource use. Sympatric populations
of two Agelenid spiders were studied for two years in a riparian
setting with the aim of characterizing their resource space
and identifying, if possible, regions of interaction or competition.
Agelenopsis kastoni and Barronopsis floridens
are similarly sized web building spiders present in relatively
high concentrations and in close proximity. At the scale of
the survey, A. kastoni were more abundant than B.
floridens. Results of field surveys suggest patterns of
vertical distribution related to size of individuals of both
species. Barronopsis move vertically as they mature
while Agelenopsis are more widely distributed on the
vertical axis as they mature. Barronopsis also tend
to be clumped and restricted to a specific set of substrates
within the habitat whereas Agelenopsis are more uniformly
distributed and more varied in substrate preferences. In order
to examine the factors affecting vertical distribution, laboratory
trials were conducted with first generation lab reared juveniles
of both species. The effects of varying intra- and inter-specific
spider density on vertical distribution were examined. (Added
6 / 17 / 2003)
|
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| Diving
Crab Spiders in the Hanging Stomachs of Borneo |
|
Author
|
Institution
|
| Simon
Pollard |
Canterbury
Museum, Christchurch, New Zealand |
|
|
Abstract:
Misumenops nepenthicola and Thomiscus callidus
(Thomisidae) are similar sized crab spiders that live within
the pitchers of pitcher plants in Asia. Anti-predator behavior
in both species includes dropping into the pitcher plant fluid,
although T. callidus will usually leave the pitcher
rather than hide in the fluid. M. nepenthicola almost
always hides in the fluid when disturbed, and can remain underwater
for up to 40 minutes. In tests with a simulated pitcher and
pitcher plant fluid, M nepenthicola remained submerged
more than ten times longer than T. callidus. This difference
may be explained by the ability of M nepenthicola,
but not T. callidus, to take a bubble of air underwater. M.
nepenthicola has a cuticular indentation or pit next to
its book lungs and the pit traps a bubble of air that covers
the book lungs while the spider is in the fluid. Because M.
nepenthicola can ‘breathe’ underwater, it can
remain in the pitcher plant fluid for extended periods of
time compared to T. callidus. (Added 6 / 18 /
2003)
|
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| Social
dynamics in an atypical social spider, Delena cancerides
(Sparassidae) |
|
Authors
|
Institutions
|
| Linda
S. Rayor |
Department
of Entomology, Cornell University |
|
Rachel
Walsh
|
| Anne
Pfeffer |
| David
Rowell |
|
|
Abstract:
The endemic Australian huntsman spider, Delena cancerides
(Sparassidae), is the most atypical of known social spiders
due to its complex social dynamics that do not fit into any
cur-rent model of spider sociality (Aviles 1997). Delena
are large non-web building spiders that live cooperatively
under bark of dead trees in dense colonies of 30 – 300
individuals. Colonies typically consist of 1 to 8 adults and
multiple cohorts of offspring. Delena share behavioral
traits with many of the cooperative spider species, but differ
behaviorally in significant ways from all of the other social
spiders (Rowell & Aviles 1995, Aviles 1997). My talk will
highlight features of social dynamics in Delena colonies
that are similar to other cooperative spiders, as well as
features are that significantly different. Delena do
not produce silk webs that facilitate cooperative prey capture
and communication. My research indicates that Delena
compensate for the lack of webs with frequent interactions
and diverse communicative behavior that is quite complex compared
to many other social species. Unlike other social spiders
that are typically indifferent to individuals from other colonies,
Delena are often highly aggressive to non-colony members.
Experiments suggest that Delena respond aggressively
to large unfamiliar individuals, but readily accept smaller
unfamiliar animals into the colony. Even among individuals
within a colony the degree of conflict and competition is
strikingly high for a social spider. Patterns of prey sharing
among mothers, non-mother adults, and immature spiders illustrate
some of these conflicts. (Added
6 / 16 / 2003)
|
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| The
Genus Sassacus (Araneae: Salticidae) North Of Guatemala |
| Author:
David
B. Richman |
| Institution:
Department
of Entomology, Plant Pathology and Weed Science, New Mexico
State University, Las Cruces |
|
|
Abstract:
The genus Sassacus s.l. ranges from southern
Canada into South America. As of present it appears to be
contained in three species groups, which may or may not be
eventually separated into their own genera. These are the
papenhoei group, the vitis group and the arcuatus
group. The Sassacus papenhoei group (Sassacus
s.s.) contains beetle mimics such as Sassacus papenhoei,
"Agassa" cyanea, and "Metaphidippus"
paiutus, as well as two undescribed species from Mexico.
The Sassacus vitis group apparently contains only one
elongated species. The Sassacus arcuatus group is more
highly developed in South America, but one undescribed species
is known from southern Mexico. The Sassacus arcuatus
group appears to contain some species with male palpal structures
intermediate between the papenhoei and vitis
groups. Courtship in Sassacus vitis and "Metaphidippus"
paiutus is very similar.(Added 5 / 24 / 2003)
|
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| Investigation
of a Brood Fostering Hypothesis that Explains Variation
in Levels of Sociality |
|
Authors
|
Institution
|
| Susan
E. Riechert |
Dept.
Ecology & Evolutionary Biology, University of TN,
Knoxville |
|
Thomas C. Jones
|
|
|
Abstract:
The exhibition of altruistic and cooperative behavior
in a world, which favors individualism and selfishness is
a problem that has been approached largely through the study
of bee, wasp and ant social systems. The social insects, however,
possess a unique mechanism of inheritance (haplodiploidy)
that makes self-sacrifice easier to achieve than in other
systems. Spiders make a better model for investigation of
the determinants of social behavior as they have the typical
diploid pattern of inheritance. We have been analyzing the
factors underlying cooperative brood care in the spider,
Anelosimus studisosus that exhibits a higher incidence
of multiple female colonies caring for a common brood at higher
latitudes and in colder local environments at a particular
latitude. A mathematical model indicates that females will
cooperatively care for a brood in those environments in which
a single female has a high probability of dying before her
offspring are able to care for themselves. The results of
initial field measures and experiments completed on spiders
from populations along a latitudinal gradient between south
Florida and Tennessee support the Brood Fostering Model of
sociality. (Added 6 / 17 / 2003)
|
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to the top of the page
|
COMPOSIÇÃO
DAS COMUNIDADES DE ARANHAS E SUAS ASSOCIAÇÕES
COM ESPÉCIES DE MYRCIA EM MANCHAS DE CERRADO
AMPLAMENTE SEPARADAS NO ESTADO DE SÃO PAULO,
BRASIL
(SPIDER COMMUNITY COMPOSITIONS AND THEIR ASSOCIATIONS
WITH MYRCIA SPECIES IN WIDELY-SEPARATED PATCHES OF CERRADO
IN SÃO PAULO STATE, BRAZIL)
|
|
Authors
|
Institutions
|
| Isabela
M. P. Rinaldi |
Departamento de Zoologia, Universidade Estadual Paulista.
Botucatu, São Paulo, Brasil |
| Luzia
A. Trinca |
|
Alan
B. Cady
|
Dept.
of Zoology, Miami University, Middletown, Ohio |
|
|
Abstract:
Brazilian cerrado is a biologically-rich, poorly understood,
yet rapidly disappearing habitat. Composition of the spider
communities from patches of cerrado located in three separate
sites in the State of São Paulo, Brazil were sampled
by beating the canopies and adjacent shrubs of three Myrcia
(Myrtaceae; "myrtle") tree species. These produced
a total of 859 spiders belonging to 21 families and 75 species.
The most undisturbed and densest cerrado patch had the largest
number of spider species, predominated by stalkers and foliage
runners. Cluster analysis (UPGMA) based on 12 sampled points
defined as different microhabitats within each patch segregated
the three sites mainly by the Myrcia species present
and geographical location of the patches. The two most similar
clusters were the areas where Myrcia venulosa was present.
The growth form of this species is more ramified than the
others, and may explain the observed spider distributions.
The presence of thomisids (Tmarus and Synema)
and the absence of the theridiid, Crysso pulcherrima,
on this plant contributed most to the similarities between
these two distant cerrado patches. Studies presenting data
such as these are important to cerrado conservation efforts.(Added
6 / 6 / 2003)
|
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| Consequences
Of Complex Display: Predator Detection Of Multi-Modal
Signaling |
|
Authors
|
Institution
|
| J.
Andrew Roberts |
University
of Cincinnati, Cincinnati, OH |
|
George W. Uetz
|
|
|
Abstract:
Signal detection theory predicts that males in complex
environments must produce signals that improve transfer of
information by being distinct from background noise. Multi-modal
signaling enhances this quality by improving detectability,
but courtship signals selected to be conspicuous to intended
female receivers become public information intercepted by
others within the signal active space, including predators.
Courtship signaling in male Schizocosa ocreata wolf
spiders occurs in multiple modes including active, sexually
selected behaviors and morphological traits that occur in
the visual and vibratory modalities concurrently. These spiders
co-occur with potential predators that may intercept courtship
signals including other wolf spiders (Lycosidae), and jumping
spiders (Salticidae). In this study, we used video/audio playback
with multiple exemplars to explore 1) whether uni-modal versus
multi-modal signals affect detection by invertebrate predators,
and 2) whether variation in a single secondary sexual characteristic,
presented as uni-modal versus multi-modal signaling affects
signal detection. Predators responded with predatory behavior
to exemplars of male S. ocreata courtship, tuft size
had a significant effect on reaction time, and the presence
of multi-modal courtship significantly facilitated detection
for at least one predatory species. (Added 6 / 6 / 2003)
|
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| Introducing
SPIDA-web: An automated identification system for biological
species |
| Authors:
Kimberly
N. Russell, Martin T. Do and Norman I. Platnick |
| Institution:
American
Museum of Natural History, New York, NY |
|
|
Abstract:
At present, the most severely limiting factor on our
understanding of community structure, diversity, and how diversity
relates to ecosystem functions and services, is the lack of
experts capable of identifying biological specimens to species.
For most groups of organisms, the number of trained systematists
is low, and the success rate of non-specialists trying to
achieve accurate identifications on their own, with currently
available tools, is even lower. The situation is worst for
relatively small and inconspicuous organisms (i.e., precisely
those groups that comprise the bulk of our planet’s biodiversity).
One way to ameliorate this problem is to encapsulate the taxonomic
expertise of a specialist in a computerized identification
system. We are currently developing an Internet-accessible
automated identification system that uses artificial neural
networks to make identifications of spider species based on
digital images of the genitalia. We call this system SPIDA-web
(SPecies IDentification, Automated and web accessible). As
our test case, we are developing the system from two perspectives:
taxonomic and geographic. For the first, we are focusing on
the recently revised Australasian family, Trochanteriidae.
For the second, we will use an ecological collection of spiders
from a site in Knox County, TN. We are still in the early
stages of this research, but early results indicate that SPIDA
will be able to classify images to genus with 95—100%
accuracy. Classification to species has proven more problematic
due to the paucity of replicate specimens, but when sufficient
numbers are available, accuracy falls in the 90—99% range.
(Added 5 / 23 / 2003)
|
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| Sharing
a Web Site: a Study of Microhabitat Selection in Latrodectus
hesperus |
|
Authors
|
Institutions
|
| Maxence
F. Salomon |
Department
of Biological Sciences, Simon Fraser University, Burnaby,
B.C., Canada |
|
Bernard D. Roitberg
|
|
|
Abstract:
When choosing a web site, a spider has to make a decision
based on an evaluation of microhabitat quality. A direct assessment
of this currency is often costly as it requires both time
and energy expenditures. As an alternative, the presence of
residents in a site may be used as an indicator of microhabitat
suitability and thereby increase the probability that other
individuals will settle there. This process may in turn lead
to the formation of localized aggregations. In southern British
Columbia, western black widow spiders, Latrodectus hesperus,
are often found to share microhabitats with conspecifics and/or
co-occuring European house spiders, Tegenaria spp.
These associated spiders seem to tolerate each other’s
existence and often form clusters of webs. In this study,
we test the hypothesis that Latrodectus hesperus spiders
preferentially settle in web sites already occupied by conspecifics
or heterospecifics rather than in empty sites, by conducting
a choice experiment in the laboratory. The results indicated
that these spiders were more likely to settle in sites containing
conspecifics than in empty ones. (Added 6 / 18 / 2003)
|
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to the top of the page
| The
Response Of Male Pardosa milvina To The Presence
Of Females And Their Cues |
|
Authors
|
Institutions
|
| Ann
Schlosser |
Department
of Zoology, Miami University, Oxford, OH |
| Ann
L. Rypstra |
|
Matthew
H. Persons
|
Department
of Biology, Susquehanna University, Selinsgrove, PA |
|
|
Abstract:
Males that incur substantial costs in locating, courting,
and mating with a female should want to find a female as quickly
and easily as possible. In order to do this, a male should
use all available cues in the environment, such as visual
and chemical, to assist in mate search and mate selection.
Pardosa milvina (Araneae: Lycosidae) is a diurnal species
with good vision and has the ability to use chemical cues
in their environment. We attempted to uncouple the use of
visual and chemical information in finding a female. In a
laboratory experiment, we measured the degree to which males
were attracted to chemical cues from a virgin female, visual
cues from a virgin female and both visual and chemical cues
from a virgin female. On average, males spent the most time
in proximity to females when both type of cues were present
followed by when only visual cues were present and the least
amount of time when no cues were present. This experiment
can assist in separating the importance of a male Pardosa’s
ability to use visual and chemical cues in mate search. (Added
6 / 17 / 2003)
|
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to the top of the page
| Kinematics
of Locomotion in the Harvestman |
|
Authors
|
Institution
|
| Andrew
Sensenig |
University
of Maryland |
|
Jeffrey
Shultz
|
|
|
Abstract:
The long legs, compact body and hanging posture of harvestmen,
coupled with the ability to rapidly traverse rough terrain,
suggest that unusual mechanics enable these arthropods to
maintain high speeds and stability. Our analyses of harvestmen
running at over 30 body lengths per second revealed near-sinusoidal
patterns of large vertical and lateral displacements of the
center of mass about the net axis of travel, with the wavelength
of the lateral sinusoid being twice that of the vertical.
A simple pendulum model of locomotion was not supported, but
instead the kinematics agreed with a spring-loaded inverted-pendulum
model. Forward velocity changed in phase with vertical displacement,
and the magnitude of the vertical motion makes harvestmen
an extreme example of an animal running in a manner predicted
by the spring-loaded inverted-pendulum model. The body of
harvestmen appears to "bounce" from one set of supporting
legs to another. The hypothesis that long legs require relatively
high mechanical energy during running was not supported. Inspired
by these findings, we hypothesize that springs within the
legs of harvestmen are loaded along both vertical and lateral
axes by gravitational acceleration of the body and that long,
multi-segmented tarsi may have evolved to enhance the storage
of elastic energy. (Added 6 / 17 / 2003)
|
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| Aspects
Of The Behavioral Ecology Of Juvenile Tarantulas Within
The Maternal Burrow |
|
Authors
|
Institutions
|
| Cara
Shillington |
Dept.
of Biology, Eastern Michigan University, Ypsilanti |
|
Brian
McEwen
|
Ypsilanti,
MI |
|
|
Abstract:
Despite their notoriety and popularity in the pet
trade, little is known about tarantulas in their natural environment.
We are involved in long term study of a large population of
tarantulas (Brachypelma vagans) in Puebla, Mexico.
In May 2003, we found juveniles along with females in six
burrows. Activities of these juveniles and the females were
observed at night. Females emerge from their burrows soon
after sunset and assume a sit-and-wait position in or near
the burrow entrance. Their burrows are lined with web and
a narrow collar of web also extends approximately 1 cm out
from the burrow entrance. Juveniles emerge from the burrow
within 30 minutes of the female and are found on the web collar.
Although the females will remain motionless for long periods
of time, juveniles are very active and there is a constant
movement in and out of the burrow. Around sunrise, females
retreat deep into the burrow after spinning a thin web covering
over the entrance. Juveniles were often found on the web collar
after the females had retreated and moved easily through the
web covering. We observed juveniles dispersing from one burrow.
Rather than a random evacuation from the burrow, juveniles
initially formed three columns and followed one behind each
other away from the burrow entrance. (Added 6 / 17 /
2003)
|
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| Molecular
Phylogeny Of Caddo And The Timing Of Phylogenetic
Events In Caddidae (Opiliones) |
|
Authors
|
Institutions
|
| Jeffrey
W. Shultz |
Dept.
of Entomology, Univ. of Maryland, College Park, MD |
|
Jerome
C. Regier
|
Univ.
of Maryland - Biotechology Institute, College Park, MD |
|
|
Abstract:
The genus Caddo has two species, C. agilis
and C. pepperella, occurring in eastern Asia and eastern
North America, a disjunct distribution also known in several
other arthropod and numerous plant groups. Two phylogenetic
hypotheses have been proposed: 1) C. agilis and
C. pepperella are each monophyletic and 2) Asian and American
C. agilis each gave rise to C. pepperella independently.
The latter hypothesis renders C. agilis paraphyletic
and C. pepperella diphyletic. The hypotheses were tested
using elongation factor-1a (EF-1a) and RNA polymerase II (Pol
II) from one representative of each species-locality combination.
The acropsopilionine caddids Acropsopilio chilensis
and Austropsopilio sudamericanus served as outgroups.
Results from analysis of third-codon positions (nt3) by parsimony
and likelihood (GTR + G model) unequivocally supported the
monophyly of C. agilis and C. pepperella.
Terminal branch lengths within and between Caddo species
were similar, suggesting that separation of Asian and American
populations occurred at about the same time due to climatic
fragmentation of a once continuous forest habitat. Molecular
clocks based on rbcL genes from 11 vascular-plant genera with
pairs of disjunctly distributed species (Xiang et al. 2000,
Mol.Phyl.Evol. 15:462-472) suggest that habitat fragmentation
and divergence within Caddo species occurred about
5.4 million years ago (mya). A log-likelihood-ratio test showed
no significance difference between the GTR + G and GTR + G
+ clock models, and the 5.4-mya date was used to calibrate
an EF-1a + Pol II nt3 clock. The
clock indicated that C. agilis and C. pepperella
diverged about 40 mya and that Caddinae and Acropsopilioninae
diverged about 90 mya.(Added 6 / 16 / 2003)
|
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| Molecular
Phylogenetics and Spinneret Evolution of RTA-clade Spiders |
|
Authors
|
Institution
|
| Joseph
C. Spagna |
University
of California, Berkeley |
|
Rosemary
G. Gillespie
|
|
|
Abstract:
The RTA clade is an extremely diverse group (~18,000
species, representing about half of the described biodiversity)
of spiders, with much variation in ecology and morphology.
The loss of the cribellum, which produces hackled silk providing
stickiness for some spider webs, has been studied in orb-weaving
spiders, but not explicitly in the RTA-clade. Using molecular
data from slow-evolving genes (1,600 basepairs 18S, 800 bp
28S), we are working to resolve relationships of some of the
more difficult-to-place three-clawed lineages in this group,
focusing on Agelenidae, Amaurobiidae, and Dyctinidae, where
taxonomy and previous cladistic analyses suggest multiple
losses, or possibly loss and secondary gain, of the cribellum
have taken place. Results of direct-optimization analysis
show a well-resolved and robust Agelenid clade that includes
the Agelenines, Tegenariines, and Coelotines, but excludes
the sole cribellate New Zealand genus represented (Neoramia).
The sister group of the Agelenid clade is a clade including
exemplars of several families, including Amaurobiidae, Dictynidae,
Cybaeidae, and Desidae, but this group is less well-resolved
and less robust to changes in tree-search parameters. The
results suggest that there have been fewer shifts from the
primitive cribellate to the ecribellate state than implied
by previous taxonomic and phylogenetic hypotheses, but further
taxon sampling will be needed to fully address this question.
(Added 6 / 17 / 2003)
|
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| Running
Performance of the Grass-Spider Hololena adnexa
on Intermittent Surfaces |
|
Authors
|
Institution
|
| Joseph
C. Spagna |
University
of California, Berkeley |
|
Rosemary
G. Gillespie
|
|
|
Abstract:
Funnel-web or grass-spiders (family Agelenidae) run
on the upper surface of their flat, sheet-ike webs. Lacking
the adhesive coatings such as cribellate silk or sticky droplets
found in the webs of other spiders, agelenids appear to rely
on speed to capture prey that stumble onto the web. Speed
is likely important for predator avoidance, and ability to
locomote off the web is important for mate searching. The
objectives of this study were to measure running performance
on various surfaces, and observe how the legs and feet of
the animals interact with the surfaces. Running performance
of 24 spiders from a local population of Hololena adnexa
was assessed on three different surfaces—metal screen
meshes with grid sizes of 7.8mm^2 and 2.0mm^2, and paper.
Performance, measured as linear speed, was not significantly
different between the three surfaces (p > .05 in paired
T-tests). Mean and maximum linear speed (44.8 body lengths/second
and 79 body lengths/second) for all runs was comparable to
literature values for fast arthropod running, when corrected
for body size. Further observation of leg-surface interactions
showed that forward progress is not impeded by failure of
the tarsus/tarsal claw to intersect with the surface, suggesting
the effective "foot" of the spider consists of more
than just the terminal leg-segments, but likely includes metatarsus
and tibia and may rely on setae for stabilization. This phenomenon
of a "distributed foot" may be broadly important
for stable locomotion in fast-running arthropods . (Added
6 / 17 / 2003)
|
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| Biogeographic
History of California Atypoides (Araneae, Antrodiaetidae) |
| Authors:
Jim
Starrett and Marshal Hedin |
| Institution:
Department
of Biology, San Diego State University, San Diego, CA |
|
|
Abstract:
The biogeography of California has many unique patterns,
one of which can be seen in the mygalomorph spider genus Atypoides.
Atypoides includes three species- A. hadros
distributed in the southeastern Ozarks, A. gertschi
distributed in the southern Cascades of northern California
and southern Oregon, and A. riversi distributed in
both the northern Coastal Range and northern Sierra Nevada
of California. Atypoides gertschi and A. riversi
are parapatric in the northern Sierra Nevada and are believed
to be sister species. Our study attempts to answer two questions
regarding the phylogenetic and biogeographic history of
Atypoides: 1) Are California Atypoides monophyletic,
as hypothesized by Miller and Coyle (1996)?, and 2) What is
the history of population and biogeographic diversification
within A. riversi? To address these phylogenetic questions,
sequence data from ribosomal and mitochondrial genes are being
generated for both populations and species of Atypoides
and related genera. 18S and 28S ribosomal data collected to
date indicate that A. gertschi and A. riversi
are not sister taxa, and that members of the genus Atypoides
form a paraphyletic grade with respect to the genus Antrodiaetus
(Antrodiaetidae). Phylogenetic divergence within A. riversi
suggests that the Central Valley has been a long-standing
barrier to gene flow, and that populations on opposite sides
of the Central Valley may indeed represent unique species.
This corroborates an early "incipient speciation"
hypothesis of Coyle (1968). (Added 5 / 8 / 2003)
|
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| Scytodes
vs. Schizocosa: Predatory Techniques And Their Morphological
Correlates |
|
Authors
|
Institutions
|
| Gail
E. Stratton |
Univ.
of Mississippi, Oxford |
|
Robert
B. Suter
|
Vassar
College, Poughkeepsie, NY |
|
|
Abstract:
Wolf spiders (Lycosidae) typically subdue prey using
their legs for capture and their fangs for the injection of
venom. Spitting spiders (Scytodidae), in contrast, subdue
prey by entangling them, at a distance, in a spitted mixture
of silk, glue, and venom that immobilizes and may also kill
them. We selected individuals of Schizocosa duplex
(Lycosidae) and Scytodes sp. (Scytodidae) of approximately
the same mass and carapace width to provide a quantitative
assessment of their relative allocations of biomass to morphological
features that might be expected to vary with prey-capture
technique. As expected, the wolf spiders allocated significantly
more to legs, chelicerae, and fangs, and significantly less
to the venom glands, than did the spitting spiders. Further
comparisons of the legs and chelicerae of the two species
provided surprises. First, the legs of Scytodes were
42% longer than those of Schizocosa despite Scytodes’s
smaller overall allocation to the legs. And second, although
the relative size of the chelicerae differ greatly, the shapes
of the chelicerae of Schizocosa and Scytodes
were not significantly different despite the radically different
tasks those structures must fulfill. (Added 6 / 17 /
2003)
|
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| Evolution
Of Water Surface Locomotion By Spiders: A Comparative
Approach |
|
Authors
|
Institutions
|
| Gail
E. Stratton |
University
of Mississippi, Oxford, MS. |
| Robert
Suter |
Vassar
College, Poughkeepsie, NY. |
|
Patricia
Miller
|
Northwest
Mississippi Community College, Senatobia, MS |
|
|
Abstract:
Spiders vary enormously in their behavior when placed on the
surface of fresh water. In some families (e.g., Theridiidae),
the spider typically becomes wet and sinks or is incapacitated
by adhesion to the water. In other families (e.g., Agelenidae),
the spider remains dry and moves across the water by walking
or running with the members of each leg pair moving in alternation
with each other. In at least one family, the Pisauridae, the
spider remains dry and moves across the water using a rowing
or galloping gait in which the members of each propulsive
pair of legs move in synchrony with each other. We tested
representatives of 249 species from 41 families of spiders
to determine their ability to move on the surface of water.
While some degree of hydrophobicity is widespread among spiders,
the ability to move on water by rowing occurs rarely in some
families but is common only among families in the Lycosoidea.
Our mapping of water surface locomotion behavior onto cladograms
of the Araneae suggests that the ability to row evolved at
the base of the clade that includes Trechaleidae, Pisauridae
and Lycosidae and evolved independently in some members of
the family Ctenidae. Rowing behavior was seen in all tested
individuals of Pisauridae, including Pisaurina spp.
and Dolomedes albineus, species not normally closely
associated with water. It is evident from our data that, in
most spiders, phylogeny trumps recent selection (based on
habitat preference) in determining the spiders' locomotor
behavior on the water surface. (Added
6 / 16 / 2003)
|
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| Scytodes:
Spitting Performance Parameters and their Biomechanical
Implications |
|
Authors
|
Institutions
|
| Robert
B. Suter |
Vassar
College, Poughkeepsie, NY |
| Gail
E. Stratton |
Department
of Biology, University of Mississippi, University, MS |
|
|
Abstract:
Spitting spiders (Scytodidae) subdue prey by entangling them,
at a distance, in a spitted mixture of silk, glue, and venom.
Using high-speed videography, differential interference contrast
microscopy, and laser-assisted oscillometry, we have begun
to measure the performance parameters that will ultimately
need to be explained in biomechanical and fluid dynamic terms.
(1) The ejection of "spit" from the venom duct (near
the proximal end of the fang) is orderly. It results in a
pattern that scans along a lateral-medial axis (due to fang
oscillations) while traversing from ventral to dorsal (due
to cheliceral elevation). Each lateral-to-medial sweep of
a fang produces silk-borne beads of glue that are not present
during each subsequent medial-to-lateral sweep. (2) The ejection
of "spit" is very rapid. A full scan (5-16 fang
cycles, one upsweep of a chelicera) typically occupies less
than 30 ms and involves fang oscillations at 500 - 1000 Hz.
We have measured ejection velocities as high as 6.3 m/s. (3)
The "spit" is contractile. During the 0.2 s following
ejection, silk shortens by 40-60% and the product of a full
scan by both of the chelicerae can exert an aggregate contractile
force of 0.1 - 0.3 mN. Based on these parameters, we offer
hypotheses concerning the biomechanical and fluid dynamic
processes that enable this kind of material ejection.(Added
5 / 23 / 2003)
|
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| Male
– Male Competition In The Wolf Spider, Pardosa
milvina (Araneae; Lycosidae) |
|
Authors
|
Institutions
|
| Patrick
L. Sutton |
Miami
University, Ohio |
|
Ann
L. Rypstra
|
| Matthew
H. Persons |
Susquehanna
University, Pennsylvania |
|
|
Abstract:
Male-male competition in nature is widely observed
because those males who are successful are more likely to
get their genes in the next generation. Pardosa milvina
(Araneae; Lycosidae) is a small, active wolf spider found
in riparian zones and agroecosystems throughout the Midwest.
Males prefer virgins to mated females and they can discriminate
from chemical cues from females. We conducted a laboratory
experiment to test the hypothesis that males will interact
more aggressively with each other in the presence of cues
from virgin females than on cues from mated females or when
no female information is present. We monitored interactions
between two males under three conditions: (1) control with
no P. milvina cues; (2) cues from a virgin female;
and (3) cues from a mated female. The males were introduced
into the testing arena, allowed to acclimate for five min.
under independent glass vials, and released. The were videotaped
for a period of 15 min and the number of aggressive acts (i.e.
touches and attacks) and the distance they maintained between
them were recorded. We found that there was a higher rate
of attacks and aggressive behavior between males on cues from
a virgin female when compared with other conditions. This
result suggests that male-male competition may have been heightened
due to the spiders’ preference for virgin female P.
milvina. (Added 6 / 18 / 2003)
|
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| Phenology
and Habitat Use by Brown Recluse Spiders (Loxosceles
reclusa) |
|
Author
|
Institution
|
| Zuleyma
Tang-Martinez |
Univerisity
of Missouri-St. Louis |
|
|
Abstract:
During Summer 2002 and Spring 2003, I studied a naturally-occurring
population of brown recluse spiders (Loxosceles reclusa)
living in the basement of my home in St. Louis, Missouri.
Observations were conducted every other night from June 2002
through June 2003. Presence and locations of spiders, as well
as daily temperatures, were recorded. Additionally, in 2003,
distance to the nearest shelter also was recorded for a subset
of spiders. Results showed that spiders first appear in small
numbers in the spring, increase rapidly and reach a peak during
the summer, and decline in the fall; no spiders were visible
during the winter months. Random observations during daylight
hours revealed that approximately twice as many spiders are
visible and active during night hours as compared to daytime.
My observations also demonstrated that spiders are predominantly
found at floor level or at very low heights near the floor,
and that they prefer sites that are near to shelter. There
appears to be extreme site fidelity (lasting days to weeks),
territorial behavior, and many sites that were used in 2002
were re-used in 2003, although not necessarily by the same
spiders. Moreover, additional observations on the main, living
floors of the house showed that, when spiders are removed,
it is common for new spiders to appear at the exact same sites
within a day to a week later. (Added 6 / 18 / 2003)
|
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| Cryptic
Costs Of Mating Under Predation Risk In The Wolf Spider
Pardosa milvina (Araneae: Lycosidae) |
|
Authors
|
Institutions
|
| Abraham
R. Taylor |
Susquehanna
University, Selinsgrove, PA |
|
Ann
L. Rypstra
|
Miami
University, Hamilton, OH |
| Matthew
H. Persons |
Susquehanna
University, Selinsgrove, PA |
|
|
Abstract:
The wolf spider, Pardosa milvina, shows effective antipredator
behavior in the presence of chemical cues (silk and excreta)
from a larger predatory wolf spider, Hogna helluo.
We examined the influence of substratum-borne predator chemical
cues on male Pardosa courtship and copulatory behavior.
Forty-one pairs of adult virgin male and female Pardosa
experienced one of two substrates: 1) a sheet of filter paper
previously occupied by an adult female Pardosa for
24 h followed by an adult female Hogna for 24 h or
2) a control sheet of paper occupied by only an adult female
Pardosa for 24 h. Using behavioral observation software
(Observer 4.1), we recorded courtship latency, duration, and
intensity (as measured by leg raise and body shake rates).
We also measured the number of successful matings, the duration
of each mating, and the number and rate of successful and
failed palpal insertions during copulation. We found no significant
difference in mating success, courtship intensity, or copulation
duration between treatments. However, males under predation
risk had significantly reduced rates of palpal insertions
and also had significantly more missed insertions than males
not under predation risk. Results suggest predation risk may
compromise sperm transfer efficiency or copulatory courtship
even when courtship and mating success appear unaffected by
the presence of predators. (Added 5 / 14 / 2003)
|
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| First
Data on the DNA Phylogeny of Some Cuban Buthidae (Scorpiones) |
|
Authors
|
Institutions
|
| Rolando
Teruel |
Museo
de Historia Natural "Tomas Romay", Santiago
de Cuba 90100, Cuba |
|
Victor
Fet
|
Marshall
University, Huntington, WV |
| Joshua
L. Greenwood |
| Matthew
R. Graham |
| Elizabeth
V. Fet |
| Dietmar
Huber |
Goefis,
Austria |
|
|
Abstract:
First data on mitochondrial DNA (16S rRNA gene) were obtained
from six species of Cuban buthids belonging to the genera
Alayotityus, Rhopalurus, and Centruroides, and
compared to the known buthid DNA sequences from the USA, Mexico,
and Dominican Republic. Rooting with Lychas (Asia)
clearly shows a separate position of Alayotityus, presumed
to be an ancient Caribbean endemic. The single Maximum Parsimony
tree (303 steps) for nine Centruroides species (rooted
with Rhopalurus) recovered a well-supported (bootstrap
82 %) "Caribbean" clade as opposed to the "North
American" clade (bootstrap 77 %). Cuban fauna of Centruroides
is confirmed as consisting of two elements: an endemic core,
and a North American element (C. gracilis), possibly
introduced. Three endemic Cuban species of Centruroides
and the Hispaniolan endemic C. bani form a topology
(C. bani (C. robertoi (C. anchorellus, C. baracoae))),
consistent with the morphology-based phylogeny suggested by
Teruel (2001), and the intensive endemic speciation on Cuba.
C. anchorellus and C. baracoae are confirmed as
separate species, with genetic distance over 16%. (Added
6 / 12 / 2003)
|
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| Laniatorid
Harvestmen in Baltic Amber (Opiliones: Laniatores) |
|
Author
|
Institution
|
| Darrell
Ubick |
California
Academy of Sciences, San Francisco |
|
|
Abstract:
Harvestmen of the suborder Laniatores have not been
well represented in Baltic amber. Until now, the only one
species has been described, Gonyleptes nemastomoides
Koch & Berendt (1854), and this based on one poorly preserved
specimen. This enigmatic species was originally placed in
Gonyleptidae, a family now occuring only in the neotropical
region, then moved to the Palpatores by Menge (1854, 1856),
and more recently transferred to Scotolemon in the
laniatorid family Phalangodidae (Star_ga 1976, 2002). A reexamination
of the type specimen now indicates that Gonyleptes nemastomoides,
although a laniatorid, belongs neither to Gonyleptidae nor
Phalangodidae, but to Cladonychiidae and thus represents the
first fossil record for the superfamily Travunioidea. Based
on the morphology of the hind claw, the species differs from
the extant genera and so probably represents a new genus.
(Added 6 / 18 / 2003)
|
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| El
Niño Influences And Colonial Orb-Weaving Spiders:
Evidence For Multi-Level Selection And Origins Of Sociality? |
|
Authors
|
Institution
|
| George
W. Uetz |
University
of Cincinnati, Cincinnati, OH |
|
J.
Andrew Roberts
|
|
|
Abstract:
Aggregations of the colonial web-building spider Metepeira
spinipes on the Monterey Peninsula in California, linked
to the 1997-98 El Niño phenomenon, present a unique
opportunity to examine mechanisms responsible for group-living
in spiders. In previous (drought) years, populations were
predominately solitary, but following the recent El Niño
event, large colonies were observed. We have now collected
data on colonies of M. spinipes from multiple sites
on the California coast, and have observed colony size distributions
and population trends over several successive years of the
climate cycle. Patterns of colonial behavior vary between
coastal sites: populations in low elevation (moist) habitats
in Monterey and Half Moon Bay show a higher proportion of
colonial individuals and stable or increasing mean colony
size; higher elevation (exposed, variable) habitats at Point
Lobos and Año Nuevo show declining proportions of colonial
individuals and decreasing or increasing colony size (respectively).
Our intensive field studies in Monterey confirm earlier observations:
increases in prey insect abundance during El Niño years
result in higher density of spider populations, creating conditions
favorable to aggregation and social behaviour. Spiders aggregate
in sites with high prey availability, and nearest neighbor
distance decreases with increased colony size. Observations
of prey availability and individual prey capture rates support
the predictions of risk-sensitivity theory: spiders living
in groups have increased prey capture and reduced variance.
Individual spiders in groups produce more egg sacs than solitaries,
and year-to-year colony size and persistence data suggest
a potential role for multi-level selection in this colonial
web-building spider. (Added 6 / 6 / 2003)
|
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| Comparative
Neuroanatomy Of Specialized Visual Processing Centers
In Two Spider Families (Lycosidae and Salticidae) |
|
Authors
|
Institution
|
| Nicole
VanderSal |
Cornell
University, Ithaca NY |
|
Damian
Elias
|
| Elke
Buschbeck |
| Ronald
Hoy |
|
|
Abstract:
Specialized visual systems have evolved multiple times
in ecologically and phylogenetically distinct families of
arachnids. Wolf spider (Lycosidae) and jumping spider (Salticidae)
visual systems in particular have become highly developed
under potentially very different light conditions, with lycosids
being active both day and night while salticids are primarily
diurnal. Consequently, jumping spiders have evolved highly
acute vision while wolf spider vision maximizes light capture
in low light conditions. Both visual systems have been studied
in detail at the behavioral, physiological and morphological
levels. Surprisingly, research on the neuroanatomy of visual
processing centers (neuropils) for principle and secondary
eyes in either of these families has been lacking. Using multiple
histological techniques, several types of optic neuropils
were found and described in both families. Each of these neuropils
has a stereotyped shape, structure and placement that do not
appear to vary across species within a family. These processing
centers are composed of multiple types of neurons, as determined
by modified Golgi methods. From the characteristic neuronal
structure of the optic neuropils, predictions were made as
to their function, based on similar structures in other arthropod
visual centers. Utilizing a comparative approach when analyzing
the neuroanatomy of different spider families, may give insight
into the functional morphology and evolution of visual specialization
under various ecological conditions. (Added 6 / 17 /
2003)
|
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| Morphological
And Molecular Systematics Of New Zealand Wolf Spiders |
| Author:
Cor
J. Vink |
| Institution:
Department
of Biology, San Diego State University,
San Diego, CA |
|
|
Abstract:
The relationship of New Zealand wolf spiders to Australian,
Asian and Holarctic genera was investigated using sequence
data from the mitochondrial 12S rRNA gene. Analysis revealed
that Australasian species form clades distinct from Palearctic
and Holarctic species providing further evidence against the
placement of Australasian species in Northern Hemisphere genera.
There is evidence that New Zealand wolf spiders are related
to a subset of Australian genera whereas the other Australian
lycosid genera are related to Asian/Holarctic faunas. The
27 species of Lycosidae found in New Zealand have been revised
and will be briefly discussed. A phylogeny for the genus
Anoteropsis was inferred using parsimony analysis of morphological
characters and contained significant phylogenetic structure.
The phylogeny of Anoteropsis was further investigated
using molecular data to test for congruence with the morphological
data and the monophyly of widespread species. Data sets from
the mitochondrial gene regions NADH dehydrogenase subunit
I (ND1) and cytochrome c oxidase I (COI) of the 20 species
in the New Zealand genus Anoteropsis were generated.
Analyses supported the existence of five main species groups
within Anoteropsis. Phylogenies generated from the
COI data set show inconsistencies with the ND1 and morphological
trees. A radiation of Anoteropsis species within the
last five million years is inferred from the ND1 likelihood
phylogram, habitat and geological data.(Added 5 / 24
/ 2003)
|
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| The
Effect of Varying Light Conditioning on Body State of
the Wolf Spider Hogna helluo |
|
Authors
|
Institutions
|
| Katrina
Waisanen |
Department
of Zoology, Miami University, Oxford, OH |
|
Ann
L. Rypstra
|
|
|
Abstract:
The wolf spider, Hogna helluo, is a known nocturnal
spider. This would suggest that they would have increased
foraging, indicated by better body condition, in a dark environment.
In order to test this hypothesis, 123 Hogna spiderlings,
aged 30-60 days, were conditioned in three different light
environments: complete dark, complete light, and a 13L:11D
cycle. Following this two-week conditioning, weight, carapace,
and abdomen measures were taken. These revealed that spiders
reared in the dark or in the light dark cycle were in better
condition than those in constant light. The spiders were then
fed four vestigial-winged fruit flies (Drosophila melanogaster)
and given 90 minutes to consume the prey. After this feeding
treatment, the previous differences in spider condition, indicated
by weight and abdomen width, disappeared. This indicates that
the spiders in the light treatment ate more than the spiders
in the other treatments. This is a surprising result for Hogna
helluo, a nocturnal spider. We speculate that this was
found because the spiders raised in the light were hungrier
than those in the other treatments, and thus, they ate more
quickly when provided with an abundance of prey. (Added
6 / 18 / 2003)
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| The
Role of the Whip in Social, Predatory, and Investigative
Behavior in an Amblypygid (Damon diadema: Phrynichidae) |
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Authors
|
Institutions
|
| Rachel
Walsh |
Department
of Entomology, Cornell University |
|
Pete
Otovic
|
| Linda
Rayor |
|
|
Abstract:
A distinctive characteristic of amblypygids is their long
antenniform first pair of legs or ‘whips.’ Whips
are used extensively to gather information about the surrounding
environment. While whips clearly play an important sensory
role, there is presently little data quantifying how amblypygid
whip and palp activity changes in different contexts. To quantify
aspects of amblypygid behavior we developed a detailed behavioral
ethogram for Damon diadema, a Tanzanian species. We
contrast the behavioral interactions of captive young and
subadult amblypygids in social, exploratory, and potentially
antipredator contexts. Whip contact is frequent between conspecifics
in amicable and agonistic contexts, and is apparently important
for both communication and localization. Young siblings are
more amicable with each other than are subadult siblings or
among unfamiliar individuals. Whip activity is significantly
more frequent when an individual is in a group than when it
is solitary. Even within an individual, if another animal
is on one side, the two whips will move at different rates.
Whip and palp movements differ when the animals are exploring
potential predators or prey, and in social contexts. Our results
document patterns and rates of behavioral interactions in
amblypygids. (Added 6 / 12 / 2003)
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| Common
Missouri Tall Grass Prairie Spiders and their Responses
to Fire and Weather |
|
Author
|
Institution
|
|
Jan
Weaver
|
University
of Missouri, Columbia |
|
|
Abstract:
I conducted a four year study of a tall grass prairie spider
community to see how different species responded to controlled
burns and weather. In March 1984, eight 30 x 30 meter plots
were established in a section of Tucker Prairie (Missouri)
that had been burned in March 1983. Four of the plots were
burned again in 1984 and all eight were sampled in August
of that year. In March 1985, another four plots were added
to the study and burned and all12 plots were sampled in August.
In 1986 and 1987, two plots burned in 1983, two burned in
1984, and two burned in 1985 were sampled in August. Sampling
was done by collecting all spiders on the vegetation and the
ground inside a 0.5 square meter quadrat. The ten most common
species over the sampling period were Wufila saltabunda
(10.3 per sample), Schizocosa bilineata (6.6), Tibellus
oblongus (4.9), Clubiona kastoni (4.2), Tmarus
angulatus (3.8), Stemonyphantes blauvelte (3.5),
Araneus pratensis (3.4), Thanatus vulgaris (2.8),
Zora pumila (2.1) and Castianeira gertschii
(2.1). The distributions of these spiders were regressed against
years since fire, and against degree days and rainfall (adjusted
to reflect deviation from 30 year means). All three independent
variables were highly correlated, so determining the relative
influence of fire and weather on individual species was problematic.
However, Wulfila saltabunda and Tmarus angulatus
were more common immediately follwing fire and declined over
time. Schizacosa bilineata was uncommon after fire
but increased in each subsequent year. Thanatus vulgaris
increased but then decreased after fire. Zora pumila
was virtually absent until the third year after fire, but
never reached very high levels. Tibellus oblongus and
Araneus pratensis were more influenced by weather than
by fire, both had higher numbers when weather was cooler and
wetter than average. For the remaining three species, neither
fire nor weather was a good predictor of their numbers. (Added
6 / 12 / 2003)
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| Behavioral
Responses of a Native Wolf Spider (Araneae: Lycosidae)
to Cues of an Introduced Predator (Mantodea: Mantidae) |
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Authors
|
Institutions
|
| Shawn
M. Wilder |
Miami
University, Oxford, Ohio |
|
Ann
L. Rypstra
|
Miami
University, Hamilton, Ohio |
|
|
Abstract:
Exotic predators are sometimes introduced into agricultural
ecosystems for the purpose of controlling crop pests. However,
studies are rarely conducted to determine if exotic predators
have negative impacts on native predators. We recorded the
behavioral responses of native wolf spiders (Pardosa milvina)
to the excreta of an exotic species of praying mantis (Tenodera
sinensis) that has been introduced for biological control.
In paired treatment arenas, P. milvina spent significantly
more time located on substrates with T. sinensis excreta
than blank controls. In addition, P. milvina spent
a significantly greater amount of time immobile and moved
at a significantly slower mean speed while on cues relative
to controls, which would reduce the probability of being detected
by a predator. The behavioral responses to mantis excreta
suggest that P. milvina may perceive T. sinensis
as a predator. Reduced activity and longer residence times
of P. milvina on cues of a larger syntopic wolf spider
(Hogna helluo) result in weight loss, lower prey capture,
and lower egg production. If T. sinensis has a negative
impact on P. milvina, then the benefit of introducing
this exotic predator for biological control may be lower than
expected. Further studies are needed on the response of other
native predators to T. sinensis and the impact of introducing
exotic predators on biological control relative to systems
with only native predators. (Added 6 / 18 / 2003)
|
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|
Impact of a Natural Catastrophe and
Subsequent Ecosystem-Level Stress on Fluctuating Asymmetry
(FA) in Wolf Spiders |
|
Authors
|
Institutions
|
| Kerri
M Wrinn |
Department
of Biological Sciences
University of Cincinnati, Cincincinnati, OH |
|
J.
Andrew Roberts
|
| George
W. Uetz |
|
|
Abstract:
Animals subject to environmental stress often exhibit developmental
instability, measured as Fluctuating Asymmetry (FA) - small,
random deviations from perfect left-right symmetry in bilateral
traits. Recent studies have demonstrated increased FA in forest-dwelling
animal populations in areas where vegetation is removed by
logging. In April 1999, a Class 5 tornado struck near Cincinnati,
causing major damage to the University of Cincinnati Benedict/Hazelwood
Botanical Preserve. Approximately half of the 65 acre forest
was destroyed, and the area is currently the site of studies
on ecosystem stress and recovery. We used FA measurement as
a means of determining the impact of this ecosystem disturbance
on populations of Schizocosa ocreata (Hentz), a common
forest-dwelling wolf spider. As FA in sexually selected male
traits has been shown to be a sensitive indicator of environmental
stress, we measured FA of foreleg tufts in male S. ocreata.
Spiders from the first post-disturbance generation were collected
in the Spring of 2000 from both disturbed and undisturbed
sites within the preserve, and preserved specimens were photographed
and measured using digital imaging. Signed (R-L) FA of male
tuft area was normally distributed with a mean of zero, indicating
‘ideal’ or ‘true’ FA, a reflection of
Developmental Instability (DI). Tuft area FA in male S.ocreata
was significantly higher in the disturbed site, suggesting
that ecosystem-level stress may produce higher levels of developmental
instability in arthropod populations. To our knowledge, this
is the first study of FA in invertebrates associated with
environmental stress from a major natural catastrophe. (Added
6 / 12 / 2003)
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| Phylogeny
Of The Burrowing Wolf Spider Genus Geolycosa: Evidence
For Rapid Morphological Evolution |
|
Authors
|
Institutions
|
| Ting
Wu |
Kent
State University Kent, OH |
|
Samuel
D. Marshall
|
Hiram
College Hiram, OH |
| Walter
R. Hoeh |
Kent
State University Kent, OH |
|
|
Abstract:
Wolf spider genus Geolycosa is fossorial burrower
in sandy area. There are total 20 species within this genus
in North America. The current classification of Geolycosa
rests mainly on Wallace’s review published in 1942. However,
relationships within the genus Geolycosa are poorly
understood. Previous to this study, the interspecific relationships
and evolutionary history of Geolycosa have not been
evaluated within a phylogenetic framework. The goals of this
study are to estimate the evolutionary relationships among
Geolycosa species within North America and recover
the underlying evolutionary processes. We used DNA sequences
from mitochondrial genes and nuclear genes, and morphological
traits in a cladistic analysis. Analyses from molecular data
and morphological data will be compared and discussed. Results
to date suggest that rapid morphological evolution has occurred
in Florida Geolycosa clade and some Geolycosa
morphospecies are not valid phylogenetic species. For taxonomic
classification to be consistent with phylogenetic relationships,
changes in the present taxonomy are necessary. (Added
6 / 17 / 2003)
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|
American
Arachnological Society 2003
27th Annual Meeting
Hosted
by Paula Cushing
Paula
may be contacted at:
E-mail: PCushing@dmns.org
Denver Museum of
Nature and Science
Zoology Department
2001 Colorado Blvd.
Denver, CO 80205-5798 USA
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