Four new species of ricinuleids are described: Pseudocellus chankin from caves and surface collections in southern Mexico (Chiapas & Tabasco) and Guatemala (Petén); Pseudocellus jarocho from a single surface collection in Veracruz, México; Pseudocellus oztotl, a troglobitic and troglomorphic species from Cueva de Las Tres Quimeras in the Sierra Negra, Puebla, Mexico; and Pseudocellus platnicki, also troglobitic and troglomorphic, known from a single cave in Coahuila, Mexico. The number of known species in the genus increases to 24, and Mexican species to 14. An identification key for adult males of the species found in Mexico and southern USA is provided.

Evarcha culicivora, an East African jumping spider (family Salticidae), was shown in an earlier study to have an affinity for the odor from two particular plant species, Lantana camara and Ricinus communis. The olfactometer used in the earlier study was designed for choice testing. Here we focus on L. camara and, by using a second olfactometer method (retention testing), add to the evidence that the odor of this plant is salient to E. culicivora. Another 17 East African salticid species, all from different genera, were investigated using the same two olfactometer designs as used when investigating E. culicivora. The number of individuals of each of these 17 species that chose L. camara odor was not significantly different from the number that chose a no-odor control and, for each species, the latency to leave a holding chamber (retention time) in the presence of L. camara odor was not significantly different from retention time in the presence of a no-odor control. Based on these findings, we conclude that, rather than being a widespread salticid characteristic, an affinity for the odor of L. camara is a special characteristic of E. culicivora.

Northwest Europe's largest heather-dominated sandy habitats are located in the nature reserve Lüneburger Heide, Germany. Yet, even these appear to be losing their ability to support some of their stenotopic species such as the ladybird spider, Eresus kollari Rossi 1846, and are thus becoming increasingly important for the preservation of these species. The habitat requirements of this endangered spider species were investigated in order to obtain data that will help stabilize the last remnants of the species' population in northwest Germany. Several heathland habitats were surveyed by pitfall trapping during the mate-search period of the males. Two statistical methods were applied: logistic regression and boosted regression trees (BRT). Both methods showed that three habitat variables are of prime relevance in predicting the occurrence of E. kollari: a) thickness of the organic layer (a negative effect), b) soil temperature at a depth of 10 cm, and c) Calluna cover in the herb layer (both have positive effect). Our results show that choppering (removing above-ground biomass and most of O-layer) and burning are likely appropriate heathland management measures for the conservation of E. kollari. Such measures improve the species' habitat quality by creating a heterogenic (small-scaled) heathland structure with suitable microhabitats. As Calluna heathlands show a clear senescence of the dominant heather, it is essential that those habitat patches be conserved. Further measures, such as transfer experiments, are recommended.

Research studies of the shallow subterranean habitats as environments for arthropods have been sparse up to this point. Using subterranean traps, we studied the distribution of spiders in soil profile over a depth span of 5–95 cm at six sites. Although almost 40% of individual specimens (1088 in total) were obtained from the epigeon (5 cm depth), spiders colonized all parts of the soil profiles examined. Beside ground-dwelling species with significant preferences for the upper layers, some species (Porrhomma microphthalmum (O. Pickard-Cambridge 1871), Centromerus cavernarum (L. Koch 1872), Cicurina cicur (Fabricius 1793), Dysdera lantosquensis Simon 1882, and Nesticus cellulanus (Clerck 1757)) commonly inhabited the whole range of the profiles studied, without any depth preference. In contrast, depigmented and microphthalmous Porrhomma microps (Roewer 1931) and Maro sp. exclusively inhabited deep soil layers adjoining void systems in bedrock.

Female-biased sexual size dimorphism is common in arthropods, apparently driven by fecundity selection in females. Selective pressures that limit growth are less often considered. One factor that researchers have rarely considered is the possible role of energetic limits on growth. The orb weaving spider Nephila clavipes (Linnaeus 1767) is extremely sexually size dimorphic. Males are “normal” sized spiders and females are up to ten times longer, having passed through several additional juvenile instars. This extreme size dimorphism presents the opportunity to test for intrinsic energetic costs of gigantism. Prior studies have shown that males successfully reach maturity on a range of diets, while female dietary requirements increase rapidly with increasing size. We here examine the effects of variation in food availability on juvenile female development by randomly assigning spiderlings from six different families (from six distinct populations) to quantitatively varying but qualitatively identical diets. Based upon field observations, we expected that dietary restrictions would have the greatest effect on duration of instars, particularly later instars, and on instar number (because longer total development would lead to curtailment of growth at an earlier stage), with relatively little effect on growth per molt. Because the diets ranged from higher than mean intake observed in the field to well below mean intake, we expected females to mature at a wide range of instars (and sizes). Our results support the functional relationship among food intake, instar duration, and fixed growth per molt (although growth per molt was less canalized than suggested by field observations). However, we observed no variation in number of instars, and we suggest that these data provide additional support for the importance of rare, large prey in the diets of web-building spiders.

Palpigradi comprises the most poorly known order within the Arachnida; hence, information regarding their biology and behavior is quite scarce. We document an interaction between a palpigrade of the genus Eukoenenia being preyed upon by a spider of the genus Metagonia in the Gruta do Vale, a cave in the municipal district of Felipe Guerra (Rio Grande do Norte, Brazil). The entire prey recognition and capture process by the Metagonia is described in full detail. Both species involved, Eukoenenia potiguar n. sp. and Metagonia potiguar n. sp., are also described. Metagonia potiguar n. sp. is the first Brazilian cave-dwelling Metagonia to be described.

Several scorpions of the genus Vaejovis in Arizona are restricted in range to mountain-top forests. These scorpions, informally referred to as the “vorhiesi complex” are very similar morphologically, but their geographic distribution has attracted the attention of several researchers, resulting in the description of a few new species in recent years. However, these species were described from small sample sizes and were diagnosed with questionable characters that were not sufficiently analyzed. This study evaluates the morphology of scorpions of the “vorhiesi complex” from seven regions in Arizona to verify the validity of the species and their accompanying diagnoses. Morphological characters examined include morphometrics, hemispermatophores, size and shape of subaculear tubercles of the telson vesicle, pectinal tooth counts, pedipalp chela denticle counts, metasomal setal counts, development of metasomal carinae, and tarsal spinule counts. New diagnoses are given for previously described species (V. vorhiesi Stahnke 1940, V. lapidicola Stahnke 1940, V. paysonensis Soleglad 1973, V. cashi Graham 2007 and V. deboerae Ayrey 2009), which are considered valid, based on the morphological evidence gathered. A new species of Vaejovis, V. electrum, is described from the Pinaleño Mountains in Arizona.

Jumping spiders (Salticidae) are known for having good eyesight, but the extent to which they also rely on olfaction is poorly understood. We report here new information on the olfactory abilities of the salticid genus Portia. We investigated for the first time the ability of adult males and females of four Portia species (P. africana, P. schultzi, P. fimbriata and P. labiata) to discriminate between mate and non-mate odor. In a Y-shape olfactometer, males of all four species chose the odor from an opposite-sex conspecific significantly more often than they chose a no-odor control, but the number of males that chose the odor from an opposite-sex heterospecific or the odor from a same-sex conspecific was not significantly different from the number of males that chose the control. The number of female test spiders that chose the odor from an opposite-sex conspecific or the odor from a same-sex conspecific was not significantly different from the number of females that chose the control. The implications of these findings for understanding Portia's mating system are discussed.

When males have high reproductive investment and female quality is variable, male assessment of sexual partners is expected. Allocosa alticeps (Mello-Leitão 1944) is a nocturnal wolf spider that shows a reversal in the sex roles and sexual size dimorphism usual in spiders. Females are the smaller, mobile sex, and they initiate courtship. Males construct burrows that serve as mating refuges and nests for female oviposition and cocoon care. In sex role reversed systems, male mate assessment is expected. Our objective was to test the occurrence of sequential male mate assessment based on female reproductive status and/or body characteristics in A. alticeps, discussing the results under sex role reversal hypotheses. We exposed males consecutively to virgin females and mated females and then recorded both courtship performance and mating occurrences relative to individuals' body characteristics. Virgin and mated females detected and entered male burrows in all the cases, and they were courted by males. However, copulations were more frequent with virgin females. The results suggest male mate selectivity in A. alticeps is based on female reproductive status. We discuss possible mechanisms underlying male mate choice in this species.

Spiders are important predators in terrestrial ecosystems, and several spider species have been shown to use chemical cues to locate prey. However, the extent to which chemical prey cues actually drive habitat use by individual spiders remains unclear. In this study we tested whether Western black widow spiders, Latrodectus hesperus Chamberlin & Ivie 1935, can detect chemical cues left by potential prey items and adjust their habitat preferences (i.e., web building behavior and refuge choice) accordingly. Using outdoor enclosures, we gave mature female widows the choice of microhabitat (rocks) previously housing cricket prey versus control rocks lacking cricket cues. Our results showed a significant preference by black widows to build their webs in areas that contain chemical prey cues. We discuss the implications of this finding for our understanding of urban black widow habitat use, population dynamics, and the potential for urban infestations.

The Leiobunum calcar species-group is erected to accommodate four species of North American harvestmen, namely, L. nigropalpi (Wood 1868), L. euserratipalpe new species, L. calcar (Wood 1868) and L. hoffmani new species. The group is characterized by several sexually dimorphic characters, including an elongate penis lacking subterminal sacs, base of male palpal tibia projecting ventrally and denticulate, and unique female sterno-opercular mechanism that appears to act as a pregenital barricade. The four species are distinguished by penial and palpal features in the male and by details of the sterno-opercular mechanism in females. The history of confusion between L. serratipalpe Roewer 1910 and L. calcar is reviewed, and the new species L. euserratipalpe is proposed to accommodate the concept of L. serratipalpe developed by North American systematists as well as the synonymy of L. serratipalpe Roewer with L. calcar. All species are diagnosed, described and illustrated, and a key to species is provided.

Four new species of salticids from the neighborhood of Lake Victoria in eastern Africa are described: Heliophanus jacksoni, Icius mbitaensis, Pseudicius athleta and Pseudicius roberti. Icius steeleae Logunov 2004 is recorded for the first time in Uganda.

The chromosome diploid number (2n) and the sex chromosome system in males of five species belonging to the families Gnaphosidae and Lycosidae were determined as 2n  =  22 (20 X₁X₂) and 2n  =  28 (26 X₁X₂), respectively. Nomisia conigera (Spassky 1941), Haplodrassus morosus (O. Pickard-Cambridge 1872) and Haplodrassus dalmatensis (L. Koch 1866) have 10 autosomal bivalents and two univalent sex chromosomes, while Pardosa bifasciata (C.L. Koch 1834) and Arctosa cinerea (Fabricius 1777) have 13 autosomal bivalents and two univalent sex chromosomes during first meiotic stages of prophase I and metaphase I. All species have acrocentric chromosomes and chiasmatic meiosis.

I describe oviposition sites and egg-hiding for four species of the family Gonyleptidae: Parampheres bimaculatus, Parampheres ronae (Gonyleptinae), Discocyrtus prospicuus, and Pachyloides thorellii (Pachylinae). Females of P. bimaculatus bury single eggs on the ground; the first record of this behavior among gonyleptids. Females of the other three species lay their eggs, singly or in clusters, on tree trunks or rock fissures. I found the eggs of P. ronae and D. prospicuus covered with debris, whereas eggs of P. thorellii were not. Females of D. prospicuus and P. thorellii lay their eggs over an extended period of time. At least for hemipterans, covering the eggs with debris works as a way to camouflage or prevent egg dehydration. I hypothesize that for the species used in this study, to spread isolated eggs in time and space may also protect them against predators and parasites.

Although relatively rare among harvestmen in the superfamily Gonyleptoidea, paternal care has been observed in the families Manaosbiidae and Gonyleptidae, but not previously in the Cosmetidae. In this study, we describe multiple observations of egg guarding by adult males of an undescribed species of cosmetid harvestman from Volcán Cacao, Guanacaste Province, Costa Rica. Observations were made from 26–28 July 2010, during the wet season. In this species, males only guard eggs after dusk, leaving eggs unattended during the day. Based upon differences in color and size, males guarded eggs through several stages of development. When guarding, males contacted the first two pairs of legs with the eggs. Oviposition sites consisted of the undersides of leaves of small plants, with eggs closely packed together in a single layer covered by abundant, transparent mucus. The largest, darkest eggs were located near the distal tip of the leaf.

Two cases of paternal care are described for species of the genus Stenostygnellus (Stygnidae), S. flavolimbatus Roewer 1913 and S. aff. flavolimbatus, both from Venezuela. Males of both species guard multiple clutches containing a large number of eggs, which are laid under rotting logs (S. flavolimbatus) or in the base of palm petioles (S. aff. flavolimbatus). These records probably represent a new and independently evolved case of paternal care in harvestmen.

A large population of Sphodros rufipes (Latreille 1829) was discovered in a municipal park in Memphis, Tennessee. We examined potential stem diameter preference, frequency of web attachment to available tree species and the spatial distribution patterns of spiders and potential attachment structures. A wide range of structure diameters were utilized for web attachment. The association of pursewebs to tree taxa was independent of the frequency of tree taxa occurrence. The spacing of vegetation stems and trunks was approximately random, but spiders exhibited a nonrandom, aggregated distribution, which was more pronounced in subadults than adults. The factors influencing S. rufipes to occur in aggregations cannot be explained by the spatial proximity of potential attachment structures in the forest.

Multilocus approaches are essential for accurately recovering the evolutionary processes underlying species and population history. However, historical inferences in non-model organisms are still almost exclusively based on mitochondrial DNA due to the difficulty of obtaining multiple informative loci. Here, we use a genomic library based approach, to generate 15 novel anonymous nuclear markers (ANMs) from the ground spider Harpactocrates globifer Ferrández 1986. The ANMs cross-amplify and sequence well in the target species and its two closest relatives, and some of them also in the more distantly related H. ravastellus Simon 1914. Levels of nucleotide diversity of the ANMs within H. globifer ranged from 0.05% to 1.4% and average sequence divergence between close congeneric relatives from 0.02% to 13.9%, supporting the utility of these loci in population and species-level analyses. Moreover, a cross-species amplification screened in other spider taxa showed that some of the loci could also potentially be useful in more distantly related genera.

Nesticus eremita Simon 1879 is naturally found in caves in southern Europe. It has also invaded and established itself in Germany and has now been found in an abandoned air-raid tunnel in Auckland, New Zealand. A diagnosis, redescription, full synonymy and illustrations are presented to aid in the identification of this potentially invasive spider.

To help to address the paucity of ecological knowledge available for Brachypelma vagans Ausserer 1875, a CITES protected species, we monitored a population in Western Belize for two years to provide data for distribution and dispersal. Despite previous over-collection for the pet trade, the species is locally highly abundant in some areas of Belize. We recorded the distribution, burrow and spider characteristics of B. vagans in 2007 and 2008 at Las Cuevas Research Station, Belize. Population dynamics were compared between years, as was individual location. Over 100 burrows were located in both years; however, previous assumptions that individuals do not move burrows regularly appear negated, since only 12 burrow locations matched between years, suggesting high intra-habitat dispersal. Despite this apparent high level of movement burrows were significantly clumped, to a similar degree, in both years. This movement could be due to disturbances throughout the year, including flooding during the rainy season. Burrow size correlated with individual body size, except in a few juveniles that appear to have opportunistically claimed an empty burrow, accounting for some small animals found in large burrows.

Ontogenetic changes in web structure occur in many spiders of different families, but the functional adaptation of differences in web structure is unknown for most species. We describe the ontogenetic changes in web structure of Leucauge argyra (Walckenaer 1842) and test the function of these differences in webs of spiderlings. Webs of early instar spiders have tangles above the orb web that vary from relatively dense to a single thread, from which some threads extend downward, connecting the tangle to the hub of the orb web. The number of threads of the tangle decreases as spiders grow, and in webs of late instars, the tangle is absent. Our experimental results indicate that the tangle and connecting threads increase the stability of the web, possibly reducing the probability of spiral threads sticking to each other with web movements.

The genus Plesiophrictus is diagnosed and redescribed based on type material and additional specimens. The type species P. millardi (Pocock 1899) is redescribed. The genus Heterophrictus is revalidated, with H. milleti as type species. Heterophrictus differs from Plesiophrictus by the absence of serrula on maxillae and by having a rastellum on the chelicerae and stiff, spike-shaped setae on the prolateral coxae I. The significance of characters used in the taxonomy of both genera is discussed.

The taxonomic status of four species of Avicularia Lamarck 1818 described from Uruguay: Avicularia anthracina (C.L. Koch 1842), Avicularia alticeps (Keyserling 1878), Avicularia parva (Keyserling 1878) and Avicularia tigrina (Pocock 1903) is discussed. The holotypes and/or original descriptions of these species were examined, and two taxonomic synonymies are needed, which are presented herein. Avicularia anthracina is transferred to Grammostola, resulting in Grammostola anthracina (C.L. Koch 1842) new combination and is considered a senior synonym of Grammostola mollicoma Ausserer 1875 new synonymy. Likewise, Avicularia parva is transferred to Catumiri Guadanucci 2004, where it is placed in the synonymy of Catumiri uruguayense Guadanucci 2004 new synonymy. Avicularia tigrina and Avicularia alticeps, originally described in the genera Ischnocolus Ausserer 1875 and Pterinopelma Pocock 1901, respectively, are herein considered nomina dubia since their types are presumed lost.

Acanthogonatus centralis Goloboff 1995 is a Neotropical nemesiid distributed in hilly zones of central Argentina. The biology of the Nemesiidae is almost unknown. We describe the courtship and mating of A. centralis based on eight observed matings (three males and five females). Male courtship involved scratching and beating the ground. These behaviors have not been observed in other mygalomorph spiders and are here described for the first time. After contacting female silk, males stretched the web. Males manipulated their pedipalps and spasmodically beat their legs over the female. The mating position was typical of mygalomorph spiders. Females remained active during copulation by making body jerks and struggling. The body jerks of females could be stimulating the male to renew palpal insertion. In addition to describing this spider family's mating behavior, we also include some notes on their shelters. The tunnel-webs observed in the field had no branches, only one entrance, and a short burrow. Adult males are capable of constructing tunnel-webs, but they are quite different from those of juveniles and females, lacking the short burrow.

The presence of buds, flowers, and fruits increases structural complexity in plants, but can also attract potential prey for predators, thus determining faunistic composition. To understand how a spider assemblage living in the shrub Byrsonima intermedia (Malpighiaceae) varies with habitat structure in terms of reproductive elements and height of plant, we collected spider specimens and measured bud, flower, fruit, and leaf masses of 44 plants, as well as their height. Spider family composition was found to depend on habitat structure, following a pattern of family turnover occurring along gradients of reproductive plant elements and height, regardless of plant biomass. Theridiidae occurred in samples with the major proportions of buds and flowers, while Oxyopidae occurred only in samples with major proportions of fruits. Multiple linear regression revealed the strong relation between the composition in reproductive plant elements and the composition in families of spiders and a relation between shrub height and spider family composition. These results help us to understand the temporal dynamics between structural complexity of vegetation and spider assemblages, because during plant phenology the proportions of reproductive elements are also varying.