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SHARING
A WEB - ON THE RELATION OF SOCIALITY AND KLEPTOPARASITISM IN THERIDIID
SPIDERS (THERIDIIDAE, ARANEAE)
by
Ingi Agnarsson
ABSTRACT.
Sociality and kleptoparasitism occur commonly in theridiid spiders.
In both behaviors a number of conspecifics occupy a single web;
gregariousness entails tolerance. Sociality has evolved several
times in theridiids, but kleptoparasitism seems to have arisen
only once. All four or more instances of sociality in theridiids
are concentrated within a clade of relatively distal theridiids.
This distribution of sociality suggests common cause, i.e. the
presence of some characteristics that may facilitate the evolution
of social behavior. The monophyletic genus Argyrodes, many
of which are kleptoparasitic, is sister to the clade containing
all social theridiids. Sociality and kleptoparasitism may thus
be phylogenetically related in theridiid spiders; behaviors that
facilitated the evolution of sociality could also have facilitated
kleptoparasitism. Both may have their roots in maternal care.
Keywords: Argyrodes,
kleptoparasitism, maternal care, social behavior
MISSING
LINKS BETWEEN ARGYRONETA AND CYBAEIDAE REVEALED
BY FOSSIL SPIDERS
by
Paul A. Selden
ABSTRACT.
Argyroneta aquatica (Clerck 1757) should be included in
Cybaeidae Simon 1898. There is no justification for a monotypic
family Argyronetidae; differences from other cybaeids are either
specializations for aquatic life or derived with respect to other
cybaeids. The features of a recently described Eocene spider,
Vectaraneus yulei Selden 2001 are discussed, which place
it together with Argyroneta in subfamily Argyronetinae
Thorell 1870 of Cybaeidae. Fossil spiders intermediate between
Vectaraneus and Argyroneta are reviewed.
Keywords: Argyronetidae,
Argyronetinae, Desidae, Eocene, England, Isle of Wight
RANGE
EXPANSION OF THE HOBO SPIDER, TEGENARIA AGRESTIS, IN THE
NORTHWESTERN UNITED STATES (ARANEAE:AGELENIDAE)
by
Craig R. Baird and Robert L. Stoltz
ABSTRACT. The hobo spider, Tegenaria agrestis (Walckenaer 1802),
was accidentally introduced into the United States probably in
Seattle, Washington during the early 1900's and gradually spread
through Washington, Oregon, Idaho and into southern British Columbia
during the 20th Century. Concurrent with the expansion in range,
there have been reports of necrosis in humans allegedly caused
by bites from Loxosceles reclusa Gertsch & Mulaik
1940 ( which does not occur in the Pacific Northwestern U.S or
Canada) or T. agrestis. The geographic range of T. agrestis
now extends into Montana, Utah, Nevada and most recently,
central and southwestern Wyoming.
Keywords: Hobo
spider, Tegenaria agrestis, Agelenidae, range expansion
DIVERSITY
OF SPIDERS IN BOREAL AND ARCTIC ZONES
by
Yuri M. Marusik and Seppo Koponen
ABSTRACT:
During the last two decades a great number of studies dealing
with arctic and boreal spiders have been published, both in the
Palaearctic and the Nearctic. Such an increase in information
makes it possible to analyze basic patterns of spider diversity
in the North as well as to show areas where further studies are
still necessary. The number of species found in faunas of larger
areas north of 60N varies from 620 (Finland) to 250 (Polar Urals)
and 300 (Yukon), when island faunas are excluded. Two areas, divided
by the Bering Strait, Northeastern Siberia and north-western North
America have marked proportion of endemic taxa (ca. 8 %) belonging
to several spider families. Considerable number of endemic spiders
are known also in Middle Siberia. The number of spiders in local
faunas of the boreal zone varies around 300 species. Study of
species composition in more than 20 local northern faunas reveals
that proportion of Lycosidae species in each local fauna varies
in smallest range (7--12 % of all species found) in comparison
to other families. Thus Lycosidae can be used as an indicator
group of general species diversity of spiders in local faunas.
Keywords: Holarctic,
diversity, indicators, northern faunas, Araneae
THE
TRIGONOTARBID ARACHNID ANTHRACOMARTUS VOELKELIANUS (ANTHRACOMARTIDAE)
by
Jason A. Dunlop and Ronny Rößler
ABSTRACT:
Anthracomartus voelkelianus Karsch 1882 from the Pennsylvanian
(Langsettian) of Nowa Ruda, Poland was listed in a 1953 monograph
by Petrunkevitch as an incertae sedis species with type
material possibly in Dresden. Antharcomartus voelkelianus
is the type species of the genus Anthracomartus Karsch
1882 and historically one of the first described examples of the
extinct order Trigonotarbida. It is a pivotal species for resolving
the systematics of both Anthracomartus and a number of
poorly defined, probably congeneric, taxa within Anthracomartidae.
Karsch's figured types were overlooked by Petrunkevitch, but have
been traced to a repository in Berlin and are redescribed here.
Additional type material from Dresden and Wroc_aw could not be
traced. One of Karsch's figured Berlin specimens is regarded here
as the holotype of A. voelkelianus, but his other figured
fossil is evidently not conspecific and is tentatively referred
here to Trigonotarbus sp. (Trigonotarbidae).
Keywords: Trigonotarbida,
Anthracomartidae, fossil, Pennsylvanian, Poland, systematics
TASMABROCHUS, A NEW SPIDER GENUS FROM TASMANIA, AUSTRALIA (ARANEAE, AMPHINECTIDAE,
TASMARUBRIINAE)
by
Valerie Todd Davies
ABSTRACT:
Three species of Tasmabrochus new genus are described.
The new species are T. cranstoni (type species), T.
montanus and T. turnerae. They are placed with Tasmarubrius
in a new subfamily Tasmarubriinae in the Amphinectidae.
Keywords: Taxonomy,
Australia, new species, Gondwanan
A
PRELIMINARY MOLECULAR ANALYSIS OF PHYLOGENETIC RELATIONSHIPS OF
AUSTRALASIAN WOLF SPIDER GENERA (ARANEAE, LYCOSIDAE)
by
Cor J. Vink, Anthony D. Mitchell and Adrian M. Paterson
ABSTRACT:A
data-set from the mitochondrial 12S rRNA gene subunit of 11 Australasian
lycosid species (six New Zealand species and five Australian species)
was generated. Three North American lycosid species, one European
species and one New Zealand pisaurid (outgroup) were also sequenced.
The sequence data for the 16 species were combined with the published
sequences of 12 European lycosids, two Asian lycosids and one
Asian pisaurid and were analyzed using parsimony and maximum likelihood
analyses. The resulting phylogenetic trees reveal that Australasian
species largely form clades distinct from Palearctic and Holarctic
species providing further evidence against the placement of Australasian
species in Northern Hemisphere genera. New Zealand wolf spiders
appear to be related to a subset of Australian genera whereas
the other Australian lycosid genera are related to Asian/Holarctic
faunas. Gene sequences in the 12S region were useful when examining
relationships between closely related genera, but were not as
informative for deeper generic relationships.
Keywords: Lycosidae,
New Zealand, Australia, lycosid genera, lycosid subfamilies
ARGYRODES: PHYLOGENY, SOCIALITY AND INTERSPECIFIC INTERACTIONS A REPORT
ON THE ARGYRODES SYMPOSIUM, BADPLAAS 2001
by
Mary Whitehouse, Ingi Agnarsson, Tadashi Mayashita, Deborah Smith,
Karen Cangialosi, Toshiya Masumoto, Daiqin Li, and Yann Henaut
ABSTRACT:
Argyrodes Simon 1864 is a large, cosmopolitan theridiid
genus whose members exhibit a wide range of foraging techniques
which usually involve exploiting other spiders, either by using
their webs, stealing their food, or preying on them directly.
We held a symposium on this genus at the 15th International Congress
of Arachnology, Badplaas, South Africa in order to obtain a clearer
perspective on the relationship between the phylogeny of the genus
and the different foraging techniques. We concluded that Argyrodes
forms a monophyletic group within the Theridiidae, and that there
are clear monophyletic clades within the genus (already identified
as species groups) that appear to share behavioral characteristics.
We found no clear indication that foraging behaviors such as kleptoparasitism
(stealing food) evolved from araneophagy (eating spiders) or vice
versa. However, it appears that species that specialize in either
kleptoparasitism or araneophagy use additional techniques in comparison
to species that readily use both foraging modes. During our examination
of Argyrodes/host interactions we noted the importance
of Nephila species as hosts of Argyrodes species
around the world and the impact of Argyrodes on Nephila.
We also noted the fluid nature of the relationship between Argyrodes
and the spiders with which they interact. For example, an Argyrodes/host
relationship can change to an Argyrodes/prey relationship,
and the type of kleptoparasitic behavior employed by an Argyrodes
can change when it changes host species. The importance of eating
silk was also noted and identified as an area for further research.
We concluded that more work involving international collaboration
is needed to fully understand the phylogeny of the genus and the
relationships between the different types of foraging behaviors.
No Keywords
ULTRAVIOLET
REFLECTANCE OF SPIDERS AND THEIR WEBS
by
Samuel Zschokke
ABSTRACT:
To determine the reflectance of spider webs and spiders under
ultraviolet (UV) light, spiders and their webs were photographed
under normal (white) light and under UV light. It was found that
all silk in araneoid webs reflect slightly more UV light than
white light; i.e., they had a positive UV-brightness. However,
the often cited, particularly high UV-brightness of stabilimenta
could not be confirmed. Spiders differed in their UV-brightness,
with most spiders reflecting less UV light than white light. Based
on the knowledge of the visual system of insects and invertebrates
it is suggested that the main function of stabilimenta is predator
defense. However, drawing a final conclusion requires more knowledge
on the way potential predators and prey perceive spiders, spider
webs and stabilimenta.
Keywords: Stabilimentum,
camouflage, predator-prey, spider silk, visibility
PITFALL
TRAPPING IN POPULATION GENETICS STUDIES: FINDING THE RIGHT "SOLUTION"
by
Shirley Gurdebeke and Jean-Pierre
Maelfait
ABSTRACT:
It is imperative to obtain a representative sample of each population
for population genetics studies. Furthermore, it must still be
possible to isolate DNA from these organisms. We adapted the pitfall
technique for that purpose after encountering severe problems
collecting sufficiently large numbers of live Coelotes terrestris
(Wider 1834) (Amaurobiidae) in the field. Although this species
is commonly caught in pitfalls, collecting them by hand proved
to be much more laborious than expected. Initially, we tested
two types of live-traps (one cup and one funnel trap) which had
been successfully used to catch carabid beetles. Both types did
not yield enough captures of C. terrestris to get a representative
sample of the studied populations. Therefore, we tested three
different killing/preservative solutions (70 % ethanol, acetic
acid + TE buffer and 4% formaldehyde) for possible use in pitfall
traps. Ethanol was the best preservative solution based on the
amount of DNA that could be isolated after treatment and on the
ability to generate the same RAPD profile as a reference DNA sample
preserved at 20 °C. To test ethanol as a preservative
solution in the field, we varied its concentration and used it
in combination with traps with or without funnels. We conclude
that it is best to use a funnel trap with 96% ethanol. We further
recommend that for every new species to be sampled in this way
an explorative investigation should be carried out determining
where, when, and how many traps should be placed (this reduces
the expense of the method). Furthermore, the effects of different
preservative solutions on the DNA of an organism of interest should
be tested. The resolution of the molecular analysis will determine
if the DNA should be of high-molecular-weight or if some degree
of denaturation is allowed.
Keywords: Pitfall
trapping, DNA preservation, Coelotes terrestris, population
genetics, Araneae
GROUND-LIVING
SPIDERS IN BOGS IN NORTHERN EUROPE
by
Seppo Koponen
ABSTRACT:
Spiders were studied in open Sphagnum bogs in Sweden, Finland
and northern Norway. Material was collected in pitfall traps.
Southern sites (hemiboreal zone) differed from coniferous taiga
sites (boreal zone, including three subzones), and also the northern
sites, north of taiga (palsa and hemiarctic zones) had their own
fauna. Typical abundant species for hemiboreal zone was Pirata
uliginosus, for boreal zone(s) Pardosa sphagnicola
and P. hyperborea and for palsa and hemiarctic zones Hilaira
nubigena and Pardosa atrata. No species was found to
be dominant and typical throughout the study area.
Keywords: Bogs,
abundant spiders, North Europe, Araneae
FINE
STRUCTURE OF MALE GENITAL SYSTEM AND SPERM IN SOLIFUGAE DOES NOT
SUPPORT A SISTER-GROUP RELATIONSHIP WITH PSEUDOSCORPIONES (ARACHNIDA)
by
G. Alberti and A. V. Peretti
ABSTRACT:
Comparative spermatology may provide characteristics that can
be useful in systematics. Previous observations on sperm structure
of the solifugid Eusimonia mirabilis revealed that the
most similar arachnid sperm cells are found within the Actinotrichida
(Acari). The general morphology of the testis and the tendency
to form sperm aggregates are also similar in both taxa. Since
knowledge of sperm in Solifugae until now came only from one species,
in contrast to Acari in which all the higher taxa have been investigated,
these characters were difficult to assess with regard to systematical
implications. The present paper confirms the derived, simple-aflagellate
structure of sperm in Solifugae and the similarity with sperm
of Actinotrichida, presenting results for two further species
of another family (Ammotrechidae) from Argentina. Sperm cells
of representatives of both taxa are small, devoid of a flagellum,
contain a chromatin body that is penetrated and surrounded by
circles of the acrosomal filament, and have a tendency to form
peripheral protuberances. Sperm morphology does not support the
frequently suggested sister-group relationship between Solifugae
and Pseudoscorpiones.
Keywords: Arachnid
sperm, comparative spermatology, sperm aggregates, systematics
THE
SUB-SAND NESTS OF YLLENUS ARENARIUS (ARANEAE, SALTICIDAE):
STRUCTURE, FUNCTION AND CONSTRUCTION BEHAVIOR
by
Maciej Bartos
ABSTRACT:
An unusual silken nest built under the sand surface is described
in Yllenus arenarius a jumping spider inhabiting
sandy dunes. In this open habitat, characterized by high temperature
and humidity gradients as well as a lack of retreats, the nest
probably plays a key role in the survival strategy of Y. arenarius
that is numerically dominant among day-active, dune-dwelling spiders.
These salticids built nests a few millimeters under the surface
after burrowing in loose sand. Four types of nests of different
size, structure and function were built: A) where eggs were laid
and early instars developed, B) where spiders molted, C) where
they overwintered and, D) the most common, where spiders spent
the night. Different age groups produced different numbers of
nests per time unit. Juveniles in their first season of life built
many more nests than subadult spiders in their second season,
which in turn built more nests than adult spiders. Various functions
of the silken nests and the high numbers built by juveniles suggest
that the structures may play an important role in surviving in
the dune.
Keywords: Salticidae,
nest, structure, function, behavior
THE
PLACEMENT OF PERILLA (ARANEAE, ARANEIDAE) WITH COMMENTS ON
ARANEID PHYLOGENY
by
Matja Kuntner
ABSTRACT:
The Oriental spider genus Perilla Thorell is revised, diagnosed
and transferred from the tetragnathid subfamily Nephilinae to
the araneid subfamily Araneinae. Cladistic analysis of recently
published araneid matrices with the addition of Perilla
supports this new placement. Perilla groups with Chorizopes
O. P.-Cambridge, previously a basal araneid. Perilla teres
Thorell, the type species of the genus, is redescribed. The only
other known species, Perilla cylindrogaster Simon, is proposed
as a junior synonym of P. teres, which renders Perilla
monotypic.
Keywords: Araneidae,
Araneinae, Nephilinae, Tetragnathidae, cladistics, spiders, Perilla,
Chorizopes
DO
INCREMENTAL INCREASES OF THE HERBICIDE GLYPHOSATE HAVE INDIRECT
CONSEQUENCES FOR SPIDER COMMUNITIES?
by
James R. Bell, Alison J. Haughton, Nigel D. Boatman, and
Andrew Wilcox
ABSTRACT:
We examined the indirect effect of the herbicide glyphosate on
field margin spider communities. Glyphosate was applied to two
replicated (n = 8 per treatment) randomized field experiments
over two years in 1997--1998. Spiders were sampled using a modified
garden vac monthly from May--October in the following treatments:
1997 comprised 90g, 180g, & 360g active ingredient (a.i.)
glyphosate ha-1 treatments and an unsprayed control; 1998 comprised
360g, 720g and 1440g a.i. glyphosate ha-1 treatments and an unsprayed
control. We examined the indirect effect of glyphosate on the
spider community using DECORANA (DCA), an indirect form of gradient
analysis. We subjected DCA-derived Euclidean distances (one a
measure of beta diversity and the other a measure of variability),
to the scrutiny of a repeated measures ANOVA design. We found
that species turnover and cluster variation did not differ significantly
between treatments. We attribute the lack of any effect to a large
number of common agricultural species which are never eliminated
from a habitat, but are instead significantly reduced. Reduction
rather than elimination does not cause the spider communities
within these plots to turn over any faster than the control. However,
like most other animal communities, the spider community did turn
over and change in structure and composition through the season,
regardless of treatment. Using Spearman rank correlations, we
found that this within-season species turnover is related to the
decline in vegetation height and the increase in percentage dead
vegetation cover in the field margin.
Keywords: Glyphosate, herbicide, spiders, species turnover, DECORANA,
field margins
GENITALIC
POLYMORPHISM A CHALLENGE FOR TAXONOMY
by
Rudy Jocqué
ABSTRACT:
Genitalic polymorphism (including polymorphism of secondary sexual
characters) is a typical example of a phenomenon that found no
place in taxonomy as there was no framework to place it. Neither
the speciation models used in ecology nor the species concept
currently in use with taxonomists "allowed" species
to have discontinuously polymorphic genitalia. Recent developments
in ecological modeling that make sympatric speciation acceptable,
and changing ideas about sexual selection, both imply genitalic
polymorphism in particular circumstances. According to the mate
check hypothesis the presence of hidden but crucial new adaptive
characters is checked during courtship and mating. Sympatric speciation
with changing behavioral characters without shifts in somatic
traits, goes through a phase of intraspecific polymorphism during
which the mating module obtains new traits backing up the newly
acquired hidden character. It implies that this speciation process
ends with the alteration of the recognition module. After the
completion of the speciation process, cases of atavism with loss
of behavioral adaptations through deleterious mutations or reversions
and reappearance of ancestral genital characters, are expected
to occur regularly. Without these, the mate check mechanism would
be meaningless. A number of examples of both types of genitalic
polymorphism in arachnids are presented. It explains why genitalic
polymorphism is rarely observed although it might be a common
phenomenon.
Keywords: Atavism,
female choice, mate check, sexual selection, species concept,
relapse, teratology
THE
FIRST GALLIENIELLIDAE (ARANEAE) FROM EASTERN AFRICA
by
C. Warui and R. Jocqué
ABSTRACT:
Toxoniella, a new genus of Gallieniellidae is described
from forest remnants on the Taita Hills in Kenya. The genus is
characterized by legs with well developed spination, the male
palp with posterior tegular extension not containing the spermduct
and the epigyne with a single central frontal ledge, double spermathecae,
and cul de sac tubes in front. Two new species, both known from
males and females, are recognized: T. taitensis and T.
rogoae. The position of the genus is discussed in the light
of the presence of enlarged piriform gland spigots on the ALS
in the male and its close relationship to Drassodella supported
by a number of synapomorphies.
Keywords: Eastern
Arc, Kenya, lamelliform hairs, piriform gland spigots
THE
OCCURRENCE OF ABDOMINAL URTICATING HAIRS DURING DEVELOPMENT IN THERAPHOSINAE
(ARANEAE, THERAPHOSIDAE): PHYLOGENETIC IMPLICATIONS
by
Fernando Pérez-Miles
ABSTRACT:
The occurrence of abdominal urticating hair types throughout juvenile
development is studied in five Uruguayan theraphosid species of
different genera. Adults of three of these species have urticating
hairs of Types III and IV while the other two species have Types
III and I. Considering spider size as an estimator of development,
Type I or IV occurred early, in small juveniles, while Type III
hairs always occurred after the other types during development.
The homology of urticating hairs and their use in phylogenetic
studies of Theraphosinae is discussed. Sexual dimorphism in the
occurrence of urticating hair types is analyzed and a hypothetical
explanation is proposed.
Keywords: Theraphosinae,
urticating hairs, theraphosid ontogeny, theraphosid phylogeny
LONG-DISTANCE
WANDERING AND MATING BY THE DANCING WHITE LADY SPIDER (LEUCORCHESTRIS
ARENICOLA) (ARANEAE, SPARASSIDAE) ACROSS NAMIB DUNES
by
Joh R. Henschel
ABSTRACT:
Adult males of the Dancing White Lady Spider (Leucorchestris
arenicola, Araneae, Sparassidae) occurring in the dunes of
the Namib Desert, Namibia, frequently wander far out of their
3m radius territories on dark nights. They move across bare dune
slopes in search of mating opportunities and subsequently return
to their burrows. In the current study, I describe the long-distance
movements and navigational ability of males and examine how their
wandering behavior relates to mating and interactions with other
males. In 16 observed complete excursions, male spiders walked
51 m (median, range 16--91 m) from their burrow along a path of
134 m (42--314 m). The return path was shorter than the outgoing
path, had less than 1/8 as many turns, and rarely retraced the
outgoing path. Typically, the return path across open terrain
had a straight section (median 33 m, range 10--89 m) which was
directed towards the home burrow with a maximum angle of deviation
of 5º. Males crossed 0--5 territories of adult males and
as many female territories, mating in about half of the encounters
with females. Males avoided each other and signaled with intense
sand drumming. Adult males differ in size and there are indications
that they compete with each other for mates by long-distance movements,
drum-signaling each other, and interfering with mating. During
three years of observations of a L. arenicola population,
8% of the largest males did 51% of the mating. Spiders of both
sexes were promiscuous, and individuals mated with each other
on several occasions. The current study prompts future investigations
concerning male orientation and its neurophysiological basis,
their ability to locate females, as well as the inter- and intrasexual
relationships of L. arenicola.
Keywords: Navigation,
orientation, homing, signaling, mating system
SPIDER
ASSEMBLAGE STRUCTURE AND STABILITY IN A HETEROGENEOUS COASTAL DUNE
SYSTEM (BELGIUM)
by
Dries Bonte, Leon Baert and Jean-Pierre
Maelfait
ABSTRACT:
An analysis of the spider assemblage structure and the presence
of indicator species in the Flemish coastal dunes are presented.
The analysis is based on data from more than 170 year-round pitfall
sampling campaigns from the 1970s onwards. We were able to find
indicator species for all identified habitats. The assemblages
are determined by variation in vegetation structure (succession),
atmospheric and soil humidity and the occurrence of both natural
of anthropogenic disturbance. In the fragmented habitats (grasslands
and grey dunes), a clear relationship was found between the mean
habitat size and the stability of the assemblage composition.
In moss dominated dunes and short grasslands total species numbers
do not increase with patch size. Due to microhabitat variation
and the possibility of attaining viable population sizes the total
number of typical species is, however, higher in larger patches.
In small patches, edge effects are more important and the number
of observed species is enlarged by the intrusion of species from
nearby habitats.
Keywords: Araneae,
indicator species, habitat size, species-area relationship
DIVERSITY
OF SPIDERS (ARANEAE) IN A SAVANNA RESERVE, NORTHERN PROVINCE, SOUTH
AFRICA
by
Cheryl Whitmore, Rob Slotow, Tanza E. Crouch, and Ansie S. Dippenaar-Schoeman
ABSTRACT:
In this study our objectives were to describe the diversity and
characteristics of spider families occurring in a range of habitat
types within a typical savanna ecosystem, to assess the influence
of habitat type and seasonality on spider diversity and to determine
levels of similarity between habitat types based on species composition.
The study was conducted at Makalali Private Game Reserve, Northern
Province, South Africa. Five different habitat types were sampled
using four trapping techniques (sweeping, beating, active searching
and pitfalls). A total of 4832 individuals including 268 species
from 38 families were sampled during the study. Families showed
varying degrees of habitat fidelity with some being widespread
and abundant while others were restricted to a single site and
were locally rare. Sites with similar habitat types showed a similarity
in spider family composition. All sites have unique species compositions
and overall diversity, evenness and richness of spiders do not
differ with habitat type. However, analyses of functional groups,
e.g., web builders and plant wanderers, showed the positive influence
of structural complexity of the habitat. The presence of unique
species in all habitats highlights the importance of conserving
as wide array of representative habitats within ecosystems. The
appearance of strong seasonal patterns in species composition
also has important implications for the development of protocols
for sampling species diversity. The savanna has a surprising diversity
of spiders when compared to other biomes surveyed in South Africa.
Factors influencing this diversity beyond the broader habitat
variables measured in this study need to be investigated.
Keywords: Diversity,
savanna, habitat types, seasonality, sampling techniques
THE
NEGLECTED COUSINS: WHAT DO WE KNOW ABOUT THE SMALLER ARACHNID ORDERS?
by
Mark S. Harvey
ABSTRACT:
An overview of the systematics of smaller arachnid orders (Opilioacariformes,
Ricinulei, Palpigradi, Uropygi, Amblypygi, Schizomida, Solifugae
and Pseudoscorpiones) is provided, along with data on numbers
of recognized families, genera and species for each group. The
micro-diverse orders, Opilioacariformes (1 family, 9 genera, 19
species), Ricinulei (1 family, 3 genera, 55 species), Palpigradi
(2 families, 6 genera, 78 species), Uropygi (1 family, 16 genera,
103 species), Amblypygi (5 families, 17 genera, 136 species) and
Schizomida (2 families, 34 genera, 205 species), are amongst the
smallest of all terrestrial arthropod orders. The meso-diverse
orders, Solifugae (12 families, 140 genera, 1,087 species) and
Pseudoscorpiones (24 families, 425 genera, 3,239 species) -- along
with the Scorpiones (1,279 species) and Opiliones (c. 6,000 species)
which are not dealt with in this contribution -- are dwarfed by
the three mega-diverse arachnid orders, Araneae (c. 36,000 species),
Parasitiformes and Acariformes (with a combined total of c. 48,000).
Keywords: Arachnida,
Opilioacariformes, Ricinulei, Palpigradi, Uropygi, Amblypygi,
Schizomida, Solifugae, Pseudoscorpiones, diversity, systematics
THE
INFLUENCE OF STARVATION ON DISPERSAL IN THE SOCIAL SPIDER, STEGODYPHUS
MIMOSARUM (ARANEAE, ERESIDAE)
by
Marilyn Bodasing, Tanza Crouch, and Rob Slotow
ABSTRACT:
Colonies of the social spider, Stegodyphus mimosarum, are
philopatric and inbred, with limited dispersal capabilities. Colony
founding events by mature males and females have been observed
periodically. We set out to test the influence of food on the
spiders' readiness to leave a colony. Thirty colonies (40 spiders
in each) were established under laboratory conditions and confined
within netting. For 31 days, 15 colonies were fed daily ad
libitum, so that the mean amount of food available was greater
than the mean requirements of the colony. The other fifteen colonies
were starved. The netting was then removed, permitting emigration
and movement from colonies was noted for two weeks. Following
risk sensitivity theory, we expected more spiders to leave the
unfed colonies due to starvation. However, a significantly higher
absolute number of spiders left colonies where food was abundant.
While fewer spiders left unfed colonies, more of these spiders
died, such that the relative number of spiders remaining at the
end of the trial was not significantly different between treatments.
Even when they were starved, the decision to leave a colony was
not based on a lack of food. Low food availability increased mortality,
yet it did not alter the remaining spiders' decision to move.
Therefore the decision to move is based on factors beyond prey
availability, which may include the state of maturity of the spiders,
the motivational state, the high cost of migration and reserves.
Keywords: Colony
founding, food availability, risk sensitivity
A
COMPARISON OF THE DIVERSITY AND COMPOSITION OF GROUND-ACTIVE SPIDERS
IN MKOMAZI GAME RESERVE, TANZANIA AND ETOSHA NATIONAL PARK, NAMIBIA
by
A. Russell-Smith
ABSTRACT:
Pitfall traps were used to census ground-active spiders in 12
different habitat types in protected savanna biomes in Tanzania
and Namibia. With roughly equivalent trapping effort in the two
areas, a total of 229 spider species and 40 families were trapped
in Mkomazi Game Reserve and 151 species and 34 families in Etosha
National Park. The family composition of the fauna of the two
areas was similar, with Salticidae accounting for 17 % (Mkomazi)
and 14% (Etosha) of all species and Gnaphosidae accounting for
16% (Mkomazi) and 14% (Etosha) of the total. Other families that
accounted for a significant proportion of species included Lycosidae
(6-7 %) and Zodariidae (6-7.5%). Despite the intensive trapping
effort, there was no indication from species accumulation curves
that a complete estimate of the spider species richness had been
obtained from either area. The possible reasons for the differences
in spider species richness and family composition in the two areas
are discussed.
Keywords: Spider
biodiversity, family composition, Etosha National Park, Mkomazi
Game Reserve
ON
THE NATURE OF AGROBIONT SPIDERS
by
Ferenc Samu and Csaba Szinetár
ABSTRACT:
Results from a 10 year survey of spiders in Hungarian arable and
natural grassland habitats are cumulated in order to reveal the
key characteristics of agrobiont species. We define agrobionts
as species that reach high dominance in agroecosystems. The most
dominant species, Pardosa agrestis, on average accounted
for 40 % of the total spider population in Hungarian arable fields.
The presence of agrobionts led to a strong skew in arable spider
community species distriibution. Regardless of the over-dominance
by agrobionts, arable spider communities had a potential for very
high species richness. The agrobiont segment of arable spider
communities showed very little field-to-field or regional variation,
i.e. the same agrobiont species occurred in all fields. Agrobionts
were indicators of arable habitats, and were rare in other habitat
types, but in many species preferences for specific natural habitat
types could be shown. These natural habitat types were often strongly
abiotically driven, frequently disturbed habitats. The life cycle
of agrobionts showed synchronization with the arable crop-growing
season. While many closely related non-agrobiont species had maturity
and reproductive periods either earlier or later than the main
crop vegetation period, agrobionts invariably reached adulthood
and reproduced during that period. Association with frequently
disturbed natural habitats and phenological synchronization with
the annual arable disturbance regime are such traits that support
the theory that agrobiont species are adapted to predictably ephemeral
habitats.
Keywords: Community
structure, arable fields, cyclic colonization, life history strategy
THE
INFLUENCE OF MOUND STRUCTURE ON THE DIVERSITY OF SPIDERS (ARANEAE)
INHABITING THE ABANDONED MOUNDS OF THE SNOUTED HARVESTER TERMITE
TRINERVITERMES TRINERVOIDES
by
Charles R. Haddad and Anna S. Dippenaar-Schoeman
ABSTRACT:
The dynamics of spiders present in abandoned Trinervitermes
trinervoides (Sjöstedt) termite mounds were studied over
a period of one year, from March 1999 to January 2000, with five
mounds excavated on a bimonthly basis. All spiders present in
the mound were collected by hand and preserved in 70% ethanol.
A total of 771 spiders represented by 21 families and 82 species
were collected from the 30 mounds during the course of the study.
The most abundant were the Gnaphosidae, which represented 37.87%
of all spiders collected, followed by the Salticidae (12.97%),
Pholcidae (10.51%) and Oonopidae (9.60%). These were the only
families that represented more than 5% of the spider fauna. The
most abundant species were Zelotes fuligineus (Purcell
1907) (Gnaphosidae) (11.69%), Smeringopus sambesicus Kraus
1957 (Pholcidae) (10.51%), Heliophanus sp. (Salticidae)
(9,86%) and a Gamasomorphinae sp. (Oonopidae) (9.21%). A correlation
was found between spider abundance and mound height, surface perforation
of the mound and season of collection. Spider numbers were highest
in mounds with a high surface degradation, while a tendency existed
for an increase in numbers with increased mound height. Web-building
spiders (Pholcidae and Theridiidae) were largely limited to mounds
with a cavity in the structure.
Keywords: Termite
mounds, spiders, mound structure
COMPARISON
OF AUTUMN AND WINTER DEVELOPMENT OF TWO WOLF SPIDER SPECIES (PARDOSA,
LYCOSIDAE, ARANEAE) HAVING DIFFERENT LIFE HISTORY PATTERNS
by
Balázs Kiss and Ferenc Samu
ABSTRACT:
Pardosa species do not over winter in the adult
stage in the Holarctic region, therefore penultimate instars should
avoid precocious maturation in autumn. We tested how artificially
increased temperature and/or lengthened light regime would affect
the pre-over wintering development of two common species with
different phenological patterns. Juvenile instars of Pardosa
agrestis (Westring 1861) and P. hortensis (Thorell
1872) were collected in autumn from the field. The experimental
spiders were held either indoor at 26 °C or outdoors at ambient
temperature and were exposed either to short or to long day length.
Molting events were monitored for five months. At outdoor temperatures
no spiders reached adulthood and molts of younger instars occurred
more frequently at long day length. In the indoor temperature
groups all P. hortensis and the majority of P. agrestis
individuals reached adulthood during the experiment. Long day
length treatment enhanced the effect of increased temperature
by almost halving the time needed to reach adulthood in both species.
Penultimate instars of both species needed at least 17 days to
molt, while earlier instars, present only in P. agrestis,
responded rapidly to higher temperature by molting. This stage
dependent response suggests that earlier instars can use favorable
autumnal temperatures to catch up with penultimate instars which
leads to higher synchrony of developmental stages in the over
wintering and spring populations.
Keywords: Life
history, overwintering, diapause, stenochronous, wolf spider
ANNUAL
DIFFERENCES AND SPECIES TURNOVER IN PEAT BOG SPIDER COMMUNITIES
by
Vygandas Relys, Seppo Koponen
and Dalius Dapkus
ABSTRACT:
The yearly differences between material collected over two years
by means of pitfall traps in three peat bogs in Lithuania and
one in Finland were analyzed. Single year collections formed 58.8--87.9%
of all the species collected over the two year period. No turnover
occurred in the abundant species (> 1% of all specimens in
one year sample) if traps were not relocated. The rates of the
turnover can vary considerably in various dominance groups and
show different trends at different sites. Marked annual differences
in abundance were recorded even among some typically abundant
peat bog species like Pardosa sphagnicola, Drassyllus pusillus,
Scotina palliardi, Agyneta cauta, Arctosa alpigena,
Bathyphantes gracilis, Antistea elegans, and Drassodes
pubescens. Only a few species typical of other habitats were
found to be permanently abundant in peat bogs. Five species recorded
during the investigation are new to the spider fauna of Lithuania.
Keywords: Araneae,
annual differences, communities, peat bogs, Finland, Lithuania
PENIS
MORPHOLOGY IN ONCOPODIDAE (OPILIONES, LANIATORES): EVOLUTIONARY
TRENDS AND RELATIONSHIPS
by
Peter J. Schwendinger and Jochen Martens
ABSTRACT:
An interim report on our ongoing revisional study is given together
with a short summary of the current knowledge on the systematics
and distribution of the family Oncopodidae (Opiliones, Laniatores).
An exceptionally high diversity in male genitalia is shown and
its possible evolution is discussed. Four major penis types are
distinguished in the Oncopodidae and compared with similar forms
in other laniatorean families.
Keywords: Opiliones,
Oncopodidae, penis types, Asia
THE
HARVESTMAN FAMILY PHALANGODIDAE 4. A REVIEW OF THE GENUS BANKSULA
(OPILIONES, LANIATORES)
by
Darrell Ubick and Thomas S. Briggs
ABSTRACT:
Two new species of Banksula are described. Banksula
incredula enlarges the concept of the genus and is assigned
to a new species group which is the likely sister group to the
other Banksula. The species is unique in numerous morphological
features, being the largest species in the genus, the first non-cavernicolous
species, and occurring in the Coast Ranges of California, rather
than in the Sierra Nevada foothills. The second new species, B.
tutankhamen, is a typical member of the californica
group but with more pronounced troglomorphy. Clinal variation
is documented for B. grahami Briggs 1974, with B.
elliotti Briggs & Ubick 1981, now placed as its junior
synonym, representing the northern and most troglomorphic populations.
Keywords: Banksula,
Phalangodidae, Opiliones, cavernicoles, California
THE
FIRST RECORD OF AMBLYPYGI FROM EGYPT
by
Hisham K. El-Hennawy
ABSTRACT:
Charinus ioanniticus (Kritscher 1959) (Charinidae)
is recorded for the first time from Egypt. Two specimens were
collected from Burg El-Arab near the Mediterranean coast, north
of Egypt.
Keywords: Amblypygi,
Charinus ioanniticus, Egypt
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