Orb spiders are commonly used to study many ecological and behavioral questions, due in part to the ease of working with their webs. The frequency distributions of prey captured by spiders are often compared among species or individuals to search for evidence of competition, effects of experimental manipulations, etc. In most instances, smaller insects are extremely common compared to larger prey, presenting a critical flaw in how such comparisons are analyzed because natural selection acts upon web evolution through the biomass, rather than total number, of prey captured. The “rare, large prey” hypothesis, developed for Zygiella x-notata (Clerk 1757), suggests that orb spiders derive the bulk of their energy not from common prey, but rather from a small subset of the largest possible insects. If correct, then orb webs should be designed to facilitate the capture of these insects, which are essential for spider fitness, even though they rarely fly into webs. Here, I test the generality of the “rare, large prey” hypothesis by comparing the frequency and biomass of large prey in 38 studies of the diets of 31 species of orb spiders in four different families. I define large prey as insects at least 66% as long as the spiders capturing them. The 38 studies included both large and small species of spiders, living in both tropical and temperate habitats. Large insects accounted for only 17% of the total number of prey captured by spiders, but contributed 85% of the total consumable biomass. The “rare, large prey” hypothesis thus can apparently be generalized across orb spiders. Future experiments need to account for the disproportionate influence of these large insects on spider fitness and on how to effectively measure these rare events. More importantly, the “rare, large prey” hypothesis provides a new framework in which to better understand variation in the web spinning behaviors of spiders.

For over 100 years, Eugène Simon's system of pholcid classification has been used with only minor modifications. Phylogenetic research over the last decade has shown that some fundamental changes are necessary if the formal system is to reflect putative evolutionary relationships. Based on cladistic analyses of morphological and molecular data and on qualitative character assessment, the family is here divided into five subfamilies: Ninetinae, Arteminae, Modisiminae, Smeringopinae, and Pholcinae. All currently valid genera are placed in a cladogram. Even though the evidence supporting some of the nodes and assignments is weak, the cladogram generates numerous testable hypotheses and provides an improved framework for the mapping of ‘new’ characters like those from sperm ultrastructure and chromosome analysis.

The Solomon Island endemic species of Charontidae, Stygophrynus (Neocharon) forsteri Dunn 1949, is transferred to the genus Charon, thus forming the new combination Charon forsteri (Dunn 1949). The subgenus Neocharon is a junior synonym of Charon. The distribution of Stygophrynus is found to be restricted to Southeast Asia from southern Myanmar to Java, not spreading east of Wallace's Line. We provide a full description, diagnosis, and numerous figures of Charon forsteri.

A long-term diet analysis of a polyphagous jumping spider Yllenus arenarius Menge 1868 (13 yr, n  =  321 prey items) was carried out in Central Poland. Due to the spider's long life cycle two cohorts are present for the whole season and for one month three cohorts coexist, which allowed me to investigate whether coexisting spiders feed on similar or different prey. Diets of spiders from these three cohorts were found to differ in three aspects: prey taxa, prey diversity and prey size. Spiders from each cohort maintained a fairly constant ratio between prey size and their own size throughout the life cycle, which resulted in dietary separation between individuals from coexisting cohorts. Such mechanisms may reduce the intensity of competitive interactions between coexisting spiders.

The urbanization process is the motor of deep environmental changes at both local and landscape levels. Although more and more studies are investigating the ecological consequences of urbanization, only a few have studied small-scale responses of biodiversity to urban-rural boundary gradients, and even fewer have compared different model groups synchronically. In this study, we compared the responses of two invertebrate groups often used as bioindicators, spiders and carabid beetles, along small-scale boundaries (around 1 km). The following parameters were estimated: assemblage composition, species richness, and activity-densities overall and per life history trait (habitat preference, dispersal abilities for carabid beetles and hunting guilds for spiders). The field data were collected in 2009 using pitfall traps set randomly in hedgerows within urban, boundary and rural zones (30 traps in total). 924 adult spiders belonging to 78 species were collected, whereas the 330 captured carabid beetles belonged to 25 species. We found no evidence of any significant change in carabid beetle activity-density (overall and for most life history traits) or in species richness along the urban-rural gradient. Conversely, there was a significant change in spider activity-density, both per habitat preference and per hunting guild. We also found a progressive change in community composition for spiders. Our results suggest that studying different model groups can provide complementary information about urbanization.

Web-building spiders form a major component of the generalist predator fauna in arable fields. They have been purported to contribute to the biological control of pests such as aphids and leafhoppers. However, their successful contribution to pest suppression is contingent upon their ability to adapt to highly-disturbed agroecosystems. We examined the population dynamics of these important natural enemies to compare phenological patterns in relation to crop cycles among species in an alfalfa agroecosystem using quadrat-based sampling and time-series analysis. Three common species of web-building spiders had generation times similar to the duration of a crop cycle (31 to 44 days), with peak abundances of adult spiders occurring at 15–18 days after harvest. The timing of these peaks corresponds with the critical early phase of the pest population cycle, during which natural enemies can have the maximum impact on pest populations, suggesting that these spiders are capable of contributing to pest suppression as part of an assemblage of natural enemies.

Sabella bavincourti Vaillant 1909 from the Eocene of northern France is a little-known trace fossil subsequently attributed – as Cteniza bavincourti – to the burrowing activities of a trapdoor spider. It is thus an ichnospecies name and not a body fossil. Its interpretation as the activity of a spider is questionable and its original assignment to a worm burrow seems intuitively more likely. Irrespective of the affinities of the producer, the ICZN also covers ichnotaxa such that classifying these structures under a modern genus name creates a homonym. It is here reassigned as the ichnotaxon Oichnus bavincourti comb. nov. Another problematic name is Theridium columbianum (Scudder 1878) from the Eocene of Canada and the USA, which is based on fossilized spider egg sacs. Under current ICZN rules fossil cocoons fall under the definition of “work of an animal”. We propose reassigning them here to Araneaovoidus igen. nov., as Araneaovoidus columbiae (Scudder 1878) comb. nov.; but stress that this is now a trace fossil name. Similar problems underlie fossilized galls attributed (probably correctly) to mites, but assigned to living eriophyid mite genera. Fossil galls are the preserved pathological reactions of plant tissue and are also not ichnotaxa sensu Bertling et al. (2006). We propose that these mite names lie outside the bounds of zoological nomenclature. Within the broader context of arachnid-related trace fossils we briefly review the literature on fossil spider webs, as well as putative arachnid trackways such as Paleohelcura Gilmore 1926 and Octopodichnus Gilmore 1927.

Although the benefits of group foraging are important for evolution of sociality in spiders, the factors that influence group-level benefits of prey sharing in social spiders are still poorly understood. In the unusual transitional social spider Delena cancerides Walckenaer 1837 (Sparassidae), prey sharing almost certainly occurs occasionally among non-kin in the wild, and so we tested the effects of kin relationships and familiarity on the amount of prey consumed in this species. To determine whether the amount of prey sharing increased with relatedness or with familiarity, we fed treatment groups containing spiderlings of varying relatedness and familiarity a single prey item and measured the amount of weight gained by sharing groups. We found no effect of relatedness or familiarity on the amount of prey consumed by prey-sharing groups of D. cancerides. Increased duration of sharing, number and age of the spiders involved, and size of the prey item all increased the amount of prey consumed. The benefits of prey sharing in this species likely overwhelm any possible inclusive fitness benefits derived from kin discrimination in this highly outbred social spider. Hence, we reject the hypothesis that groups of kin consumed proportionately larger amounts of prey biomass than groups of non-kin, as proposed by Schneider and Bilde in 2008 with Stegodyphus lineatus Latreille 1817 (Eresidae).

We investigated the influence of burning frequency and timing on the abundance and diversity of cursorial arachnids in the cerrado (savannah of central Brazil). Five areas were subjected to different burning regimes. In each area, 40 pitfall traps were installed. The arachnids were sampled for three days each month from April 2007 to October 2008. Abundance was higher in the control area than in areas subjected to any fire regime. Species richness was similar in all areas. The evenness was lower in the control area. The areas subject to fires had significantly higher diversity than the control area. Although it was not possible to rank areas according to their diversity, areas burned in the middle of the dry season tended to have higher diversity than areas burned at the beginning or end of this season, indicating that the time at which fire occurs may be more important than the frequency of burning for the diversity of cursorial arachnids in the Brazilian cerrado.

Four new species of Xenocytaea: X. stanislawi, X. taveuniensis, X. victoriensis, and X. vonavonensis are described from Fiji and the Solomon Islands. X. anomala Berry et al. 1998 is excluded from the genus. The remarks on distribution and relationships are compared with literature data.

The family Hexisopodidae is endemic to southern Africa. Hexisopodids represent a very peculiar group of Solifugae. They differ from all other solifuge families through various autapomorpic adaptations to a subterranean mode of life, most notably the presence of fossorial legs. The phylogeny of the Solifugae is widely unresolved. The ultrastructure of spermatozoa has successfully been used for phylogenetic analyses in other animal taxa. Therefore, the question arose whether the morphological peculiarity of the family Hexisopodidae might also be reflected in the ultrastructure of their spermatozoa. This was investigated for Hexisopus psammophilus Wharton 1981 (Hexisopodidae). Spermatozoa do not seem to aggregate in the testes, nor in the vasa deferentia. Sperm cells are aflagellate, roundish, and with irregularly shaped chromatin bodies. Each sperm is surrounded by a secretion sheath, thus representing a typical cleistosperm, the first record of this form of sperm transfer in solifuges. The sperm cells form finger-like protuberances and contain putative granules of glycogen, features shared with the Ammotrechidae, Daesiidae and Solpugidae. The acrosomal complex shows additional similarity with the Solpugidae. Overall, the spermatozoa of H. psammophilus share some morphological features with the Ammotrechidae and Daesiidae, but mostly resemble that of the family Solpugidae.

Although the diversity of spider orb web architectures is impressive, few lineages have evolved orb webs larger than 1m in diameter. Until recently, such web gigantism was reported only in a few nephilids and araneids. However, new studies on bark spiders (Caerostris) of Madagascar report a unique case of web gigantism: Darwin's bark spider (C. darwini) casts its webs over substantial water bodies, and these webs are made from silk whose toughness outperforms all other known spider silks. Here we investigate C. darwini web architecture and provide data to begin to answer two intriguing questions to explain these extraordinary web characteristics: 1) Are C. darwini webs specialized to subdue unusually large, perhaps even vertebrate, prey? 2) Do these large, riverine webs allow the spiders to capitalize on catching numerous small semi-aquatic insects? During fieldwork in Madagascar, we studied C. darwini web architecture and ecology, as well as interactions with prey. We characterize C. darwini webs as having relatively simple capture areas with very open sticky spirals and few radial lines. We also compare web features in several sympatric Caerostris species, among which C. darwini represents the most extreme case of web gigantism, with the largest orbs up to 2.76 m² and longest bridge lines reaching 25.5 m. While preliminary, current data suggest that C. darwini webs are effective snares for semi-aquatic insects such as mayflies and dragonflies, while vertebrate prey were never observed. We suggest that mass emergence of aquatic insects may function analogously to the capture of rare, large prey that recent studies suggest are critical for reproduction in orb weaving spiders.

The global demand for different land-use practice commodities in the Amazonia is growing, and this region is increasingly affected by the impacts of land management. The aim of this study was to evaluate the influence of land-use intensification on soil spider assemblages from six different land-use systems in Colombia and Brazil. The systems were fallows after crops and pastures, forest, crops, pastures and plantations. Spider species richness and density decreased with increasing farming management intensity. A principal component analysis (PCA) showed forests and fallows were separated from systems with stronger anthropogenic soil disturbance. The relationships of ten spider guilds differed significantly between land-uses, suggesting that they can be a reliable parameter for studies of ecological indicators.

A new, eyeless species of harvestman, Paranemastoma beroni, collected from the Stoykova Dupka 1 Cave in the Slavyanka Mountains (south-western Bulgaria) is described and illustrated. A character combination of the form of the penis, the form of the pedipalps and absence of scutum armament, distinguish the new species from all other Paranemastoma species. The closest morphological relative, and the only other eyeless example, is the troglobiont P. bureschi (Roewer 1926), which is allopatric (north-western Bulgaria) and clearly differs in the presence of scutum armament and lack of cheliceral apophysis and opening of the cheliceral gland. Characterization and comparison of sculpture in non-troglobiont and troglobiont Paranemastoma species and SEM illustrations are included. A case of cuticular neoteny in troglobionts is also reported.

The genus Oligoxystre was originally established in 1924 for O. auratum Vellard 1924 from southern state of Goiás, Central Brazil. Today, the genus includes seven species: O. auratum, O. caatinga Guadanucci 2007, O. bolivianum (Vol 2001), O. tucuruiense Guadanucci 2007, O. rufoniger Guadanucci 2007, O. dominguense Guadanucci 2007, and O. diamantinensis Bertani et al. 2009. Oligoxystre mineirum new species, from the Atlantic forest domain is described here. The cladistic analysis resulted in a single tree: (O.caatinga (O.mineirum ((O.tucuruiense O.rufoniger) (O.diamantinensis (O.bolivianum O.dominguense))))). According to the area cladogram obtained, it is possible to draw the following conclusions: the origin of the Cerrado fauna is monophyletic; the occurrence of two sympatric species in Caatinga is due to different events; and the diversity of Oligoxystre in Serra do Espinhaço (O. rufoniger, O. diamantinensis and O. mineirum) is probably the result of the contact of the typical fauna of each bioma (Cerrado, Caatinga and Atlantic Forest).

Detailed morphologies of the male copulatory organs of the Australian genera Anzacia, Intruda, Encoptarthria and Zelanda and the Holarctic genus Drassodes are presented. The homology of several palpal elements within the family Gnaphosidae is established. The possible homology of these structures with those in other spider families is discussed. The ground plan of the gnaphosoid genital bulb is compared with the bulb of other Entelegynae genera. Australasian spider genera have a peculiar organization of the male palpal organs. Thus, the Holarctic genus Drassodes was also analyzed for comparison. The analysis of the male copulatory organs is presented and its implication for classification of these groups is discussed. The taxonomic changes we make here are the transfer of four species from the genus Megamyrmaekion to genus Encoptarthria: E. echemophthalma (Simon 1908), E. penicillata (Simon 1908), E. perpusilla (Simon 1908), and E. vestigator (Simon 1908). One species is transferred from genus Echemus to genus Encoptarthria: E. grisea (L. Koch 1873). New synonymy established: Encoptarthria echemophthalmum (Simon 1908)  =  Encoptarthria serventyi Main 1954, syn. n.

The family Araneidae is the third largest among spiders and the third most studied from a cytogenetical point of view. In spite of this, only 2% of all araneids have been karyotyped. The majority of araneids analyzed possess 2n  =  24 chromosomes in males; however, the study of additional species could reveal unusual karyotype characteristics. Thus, the aim of this work is to analyze chromosomally, for the first time, six species belonging to three araneid genera from Brazil. The specimens of Alpaida leucogramma (White 1841), Alpaida truncata (Keyserling 1865), Alpaida veniliae (Keyserling 1865), Parawixia kochi (Taczanowski 1873), Parawixia velutina (Taczanowski 1878) and Wagneriana sp. were collected in Parque Nacional de Ilha Grande and in the municipality of Rio Claro. The gonads were treated with colchicine and hypotonic solution before fixation with Carnoy I solution. The results were 2n♂  =  24 (11II X₁X₂) in A. leucogramma and P. velutina, and 2n♂  =  22 (10II X₁X₂) in A. truncata, A. veniliae, P. kochi and Wagneriana sp. When the chromosomal morphologies were established, we observed telocentric chromosomes in all specimens save one female specimen of P. velutina. The univalent sex chromosomes were easily recognized on diplotenes. The unpaired metacentric element found in one female specimen of P. velutina with 2n  =  25 probably arises by centric fusion/fission. Araneidae is a megadiverse family composed of ∼3000 species distributed mainly in the tropics; thus the analysis of more species may provide new insights about orb-weaver chromosome evolution.

Records of mites parasitizing pseudoscorpions are summarized and new host-parasite associations are reported. Trombidium brevimanum (Berlese 1910) (Trombidiidae) has been found on Neobisium bernardi bernardi Vachon 1937 in France (new country record for T. brevimanum), and T. mediterraneum on N. carcinoides (Hermann 1804) in Norway (new country record for T. mediterraneum). These are the first cases in which both the mite and the pseudoscorpion have been identified. An additional record of Trombidium sp. (probably T. mediterraneum) on Neobisium fuscimanum (C.L. Koch 1843) is given from Poland. A previously unpublished record of a Leptus larva on a pseudoscorpion, possibly belonging to the genus Neobisium, is noted from France. Parasitism of Roncus lubricus L. Koch 1873 by an unidentified larva of Parasitengona (probably Trombidiidae) is also noted from Germany. The stylostomes (feeding canals) formed in pseudoscorpions by trombidiid mites are similar to those produced in other hosts. Scars in the pleurum of the pseudoscorpions are interpreted as the result of attempts at fixation by the mite larvae. Pseudoscorpions appear to represent alternative hosts for Trombidium larvae, although the successful completion of development has yet to be demonstrated.

New records of parasitic Parasitengona larvae on harvestmen hosts from the Palaearctic region are provided. Four species of harvestmen have been found to be new hosts of Parasitengona and four species of mites have been recorded as new parasites of Opiliones. The first case of parasitism of Hydrachnidia on harvestmen has been found.

New data are provided on larvae of terrestrial Parasitengona mites parasitizing spiders. Larvae of Erythraeidae and Trombidiidae are recorded as parasites of spiders representing five families. Members of Philodromidae and Tetragnathidae (Pachygnatha clercki Sundevall 1823) are reported as hosts of Trombidioidea for the first time. The available information indicates that some Trombidiidae have a narrow host range with affinity to spiders, whereas the Erythraeidae are more opportunistic parasites.

We studied occurrence and morphological adaptations of two species of Porrhomma down to 135 cm soil depth. Porrhomma microps Simon 1884 inhabited soil layers at depths between 5 and 135 cm. Porrhomma aff. myops was found at depths of 35–95 cm. Specimens of both species were depigmented and had highly reduced eyes. Compared with the epigean P. pygmaeum (Blackwall 1834), P. myops, which inhabits scree and caves, exhibits significantly longer legs. We interpret it as an example of troglomorphism. Compared with the epigean P. pygmaeum, P. aff. myops is found deep in the soil and exhibits a significantly smaller cephalothorax. We interpret this as edaphomorphism. We assume the edaphomorphic population of P. aff. myops to be permanent soil dwellers.

Most orb webs are vertically asymmetric with the hub above the geometric center, even though the basic structure of orb webs with concentric sticky spiral loops implies a round shape with the hub in its geometric center. Spiders are known to modify the basic, round web structure to achieve asymmetric webs by placing the sticky spiral loops eccentrically around the hub and by inserting partial sticky spiral loops below the hub. In addition, spiders could increase asymmetry with larger spiral spacing below the hub than above. In the present paper, I analyzed these web modifications quantitatively in webs of Araneus diadematus Clerck 1757. In addition, I assessed the influence of gravity on the different web modifications during web building by laying some webs horizontally during auxiliary and/or sticky spiral building, and I also assessed how the web modifications affected each other during web building. I found that web orientation during auxiliary spiral building influenced auxiliary spiral eccentricity, which in turn had an impact on sticky spiral eccentricity and overall web asymmetry. Web orientation, together with web asymmetry and spiral ratio, during sticky spiral building only influenced spiral spacing asymmetry. I conclude that A. diadematus uses the auxiliary spiral as a guiding line during sticky spiral building and that it applies different rules to build the two spirals.