Abstracts to Articles

The Journal of Arachnology

Volume 30 Number 2

The Proceedings of the 15th Internal Congress of Arachnology

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

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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

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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

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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

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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

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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

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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

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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.

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

 

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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

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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

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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

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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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This page was posted 11 / 13 / 2002 and modified 11 / 27 / 2009