A desert-living spider sparassid (Cebrennus rechenbergi Jäger, 2014) and several lycosid spiders (Evippomma rechenbergi Bayer, Foelix & Alderweireldt 2017, Allocosa senex (Mello-Leitão, 1945), Geolycosa missouriensis (Banks, 1895)) were studied with respect to their burrow construction. These spiders face the problem of how to transport dry sand and how to achieve a stable vertical tube. Cebrunnus rechenbergi and A. senex have long bristles on their palps and chelicerae which form a carrying basket (psammophore). Small balls of sand grains are formed at the bottom of a tube and carried to the burrow entrance, where they are dispersed. Psammophores are known in desert ants, but this is the first report in desert spiders. Evippomma rechenbergi has no psammophore but carries sand by using a few sticky threads from the spinnerets; it glues the loose sand grains together, grasps the silk/sand bundle and carries it to the outside. Although C. rechenbergi and E. rechenbergi live in the same environment, they employ different methods to carry sand. Geolycosa missouriensis lives in a moister habitat and produces solid sand pellets in which sand grains are caked together (without silk threads); the compact pellets are flung away from the burrow entrance by a rapid extension of the first legs. The spiders stabilize the developing tube inside by repeatedly adding silk rings, while digging down. This wall is very thin, consisting of only a few layers of crisscrossing silk threads. An excavated burrow collapses immediately, indicating that the stability is not due to the silk. Instead, the tight interconnection of neighboring sand grains—as in a vault—yields the necessary solidity to the burrow.

The navigation by scene familiarity hypothesis provides broad explanatory power for how bees and ants navigate from the hive to distant food sources and back. The premise is that the visual world is decomposed into pixelated matrices of information that are stored and readdressed as the insects retrace learned routes. Innate behaviors in these insects (including learning walks/flights and path integration) provide the important goal-directed views to allow the initial retracing (i.e., the insect must learn the scene while moving toward the goal because everything looks different while moving away). Scorpion navigation may use a similar premise, with the chemical and textural features of the environment substituting for visual input. Scorpion pectines support thousands of chemo- and mechano-sensitive units called peg sensilla, each containing at least 10 energetically expensive sensory neurons. We have long wondered why pectines have so many pegs and associated neurons. Many sand scorpions emerge onto the surface from their home burrows at night to pursue insect prey and somehow find their way back to their burrows. Based on the measured resolution of peg sensilla, we have calculated that sufficient information exists in sand's texture to enable scorpions to retrace previously experienced paths with little to no chance of confusion. Preliminary evidence of learning walks and path integration in scorpions is also congruent with the navigation by chemo-textural familiarity hypothesis.

Retreat selection is critical for animals that spend much of their diel cycle in retreats. At issue is how retreat availability and social dynamics interact to influence whether retreats are defended from or shared with conspecifics. The prolonged subsocial huntsman spider, Delena lapidicola (Hirst 1991, Sparassidae), lives in family groups under rock retreats which are relatively abundant on granite headlands in Western Australia. Their more social congener, D. cancerides (Walckenaer, 1837), lives in rare retreats under the bark of trees in southern Australia. We tested retreat sharing patterns with kin and non-kin in D. lapidicola, and of unrelated adult female D. cancerides using laboratory assays. For each trial, two spiders were introduced 12-hr apart in a large arena with two retreats and given 24-hr to share a retreat or occupy their own retreat. Aggression and mortality were recorded. In this study, 42% of D. lapidicola shared retreats regardless of kinship, age, sex, mass or natal colony. Even adult females shared retreats peacefully. Aggression only occurred once. In stark contrast, no D. cancerides adult females shared retreats and 36% of the trials resulted in mortality or serious injury. Our results support the hypothesis that an abundance of retreats in D. lapidicola habitats reduces pressure to defend and allows sharing with little discrimination of kinship, while the rarity of retreats in D. cancerides habitats results in aggressive defense.

During the winter of 2014–15 in southern California, attempts were made to accelerate immature brown recluse spiders, Loxosceles reclusa Gertsch & Mulaik, 1940, to maturity for a pest control experiment in early spring. Despite food offerings, spiders stopped molting after October although they were maintained at 25° C and had swollen, well-nourished abdomens. It was surmised that decreased filtered daylight from a paper-covered window might be suppressing molting. Feeding was halted in January 2015; 88 spiderlings were checked weekly for molts. Molting resumed during late March 2015 and continued through May 2015 despite no feedings. To more thoroughly elucidate photoperiod effects on molting, during the week of the September 2015 equinox, three cohorts of 10 immatures of both brown and Chilean recluses, L. laeta (Nicolet, 1849), were exposed to three light regimes: 14:10 L:D, natural, 10:14 L:D. Through November 2015 to late March 2016 for brown recluses, there was no molting in the 10:14 regime, 3 of 10 spiders molted in the natural light regime, and 8 of 10 spiders molted in the 14:10 L:D regime. Additionally, fifteen newly-emerged brown recluse spiderlings split into three cohorts of 5 spiders each in November exhibited more molting in the 14:10 L:D compared to natural and 10:14 L:D light cycles. Chilean recluses showed no differences in molting across the three photoperiod regimes. This species difference may be explained in that brown recluses are native to temperate zones where winters can be fatal; Chilean recluses are tropical where short photoperiods may have little significance for survival.

Based on studies of adult behavior, the desert spider Agelenopsis aperta (Gertsch, 1934) is considered exemplary of a species exhibiting an aggressive syndrome. This study offers a first examination of the nature of interactions that juvenile A. aperta engage in during the period when sibs are clustered on a group web. We test the hypothesis that early instar A. aperta lack the aggressiveness noted for older instars. Our data set is comprised of observations of five weekly feedings offered to 818 sibling pairs, constituting an average of 4.6 replicate sib pairs from each of 174 families. At each weekly feeding, a worker termite was offered to each sib in the shared container in which they had built web retreats. We observed no cooperative foraging during the course of these feedings. Rather, most families exhibited a mix of independent foraging and non-injurious contests over prey. We present a brief overview of the occurrence and initiation of contests over prey, with particular reference to the weekly feeding in which contests first occur versus the feeding in which a seminal contest takes place (i.e., where sibs earn permanent winner versus loser status).

A new species of trapdoor spider of the genus Liphistius Schiödte, 1849 (Mesothelae: Liphistiidae) is described from specimens collected from Mae Wong National Park, Klonglan district, Kamphaeng Phet province, Thailand. This Liphistius species belongs to the bristowei species-group based on the elevated cumulus and the distinct embolic part, and resembles L. yamasakii Ono, 1988. Diagnostic characters of the male and female are discussed, and a map is provided for the type localities of the 32 previously described Liphistius species in Thailand. This is the first record of a Liphistius species in the bristowei species-group that builds a T- or Y-shaped burrow with two trapdoor openings.

The widespread and previously monotypic genus Misumessus Banks, 1904 from North America is found to consist of at least seven species. The type species, M. oblongus (Keyserling, 1880), occurs from Ontario, Canada, to eastern Texas and ranges over most of the eastern and mideastern United States. Misumessus lappi sp. nov. has a midwestern range and is known from central Texas to eastern Colorado. Misumessus dicaprioi sp. nov. is recorded from western North America from California, Utah and western Colorado, south to Arizona, New Mexico, and southwest Texas. Misumessus tamiami sp. nov. occurs in the southern half of peninsular Florida. Misumessus quinteroi sp. nov. is circum-Caribbean, with records from Mexico to Panama, Trinidad, and the Greater and Lesser Antilles. Another Antillean species, M. bishopae sp. nov., is known from Puerto Rico, Dominica, and possibly the Grenadines. Misumessus blackwalli sp. nov. is known from Bermuda from a single male; it is unlikely that this species represents Thomisus pallens Blackwall, 1868, a nomen dubium based on a juvenile female, and the only thomisid previously reported from Bermuda. This name has not been used since the 19^th century other than in catalogs and checklists, and since its retention could potentially create a homonym, it is declared a nomen oblitum. The epigynal ‘hood' of thomisids is considered misnamed, as it engages the retrolateral tibial apophysis (RTA), and is renamed the ‘coupling pocket' as in other RTA clade members. A hood is herein considered to be a general term that refers to an epigynal outgrowth partly enclosing a depression that engages a structure on the palpal bulb rather than the palpal tibia.

Fossils from the mid-Cretaceous (c. 99 Ma) Myanmar (Burma) amber include all extant orders of Arachnida, including the earliest representatives of Schizomida, Parasitiformes, and Palpigradi. Schizomids are figured from Burmese amber herein for the first time. The most abundant and diverse arachnid order is the Araneae, with 38 families, 93 genera, and 165 species recorded to date. The araneofauna is dominated by haplogynes and palpimanoids, whilst araneoids are rare and members of the RTA clade absent. The arachnofauna is typical of a tropical rainforest habitat, which concurs with evidence from other Burmese amber biota.

A new species of the lycosid subfamily Evippinae is introduced and preliminarily assigned to the genus Evippomma Roewer, 1959. It was found in the Erg Chebbi Desert in Morocco. Evippomma rechenbergi sp. nov. is a wolf spider with unusual morphological and behavioural features, e.g., having exceptional scales on most of its body and carrying sand by interconnecting sand grains with silk threads. A detailed description and delimitation of this species is given. Its genus-affiliation is found uncertain. We conclude that a comprehensive revision and phylogenetic study of all African genera of the subfamily Evippinae are needed to enable unambiguous identification (including unambiguous genus identification) and for a better understanding of phylogenetic relationships among these genera.

The timing and nutritional value of a first meal is important for spiderlings, but little is known about what spiderlings specifically consume. For wandering spiders, nectar feeding is a common occurrence thought to be directly beneficial in providing nutrients and serving to fuel energy costly for foraging. Cannibalism is also prevalent among many spiders. We suspect in spiderlings of the cursorial species, Oxyopes salticus Hentz, 1845, nectar feeding could decrease cannibalism by causing satiation, or increase cannibalism by enhancing energy levels and rates of interaction. We conducted laboratory experiments to test the longevity of newly hatched O. salticus in the presence of different nutrient resources and the effect these resources had on cannibalism rates. Spiderlings were housed solitarily or in pairs and given access to different nutrient resources that reflect those available in the wild, including nectar and insect prey items (fructose, protein, and water). In a 14-day period, we recorded the number of days each spiderling was alive to determine survivorship. By the end of the experiment, 60% of spiderlings housed with fructose were still alive and 10% survived when housed with protein or water. Based on survivorship models, the predicted mean age at death differed between treatments (15.9 days for fructose, 11.2 days for protein, and 9.5 days for water). Spiderlings housed in pairs declined more rapidly in survivorship compared to solitary spiderlings, suggesting cannibalism occurred across all treatments. Fructose significantly increased longevity of spiderlings regardless of their housing and reduced cannibalism.

The wasp spider Argiope bruennichi (Scopoli, 1772) is of Mediterranean-Pontian origin, but for decades it has been expanding northwards, including into the territory of Poland. Based on well-documented expansion records, we can distinguish “old” (south-eastern and south-western) and “new” populations (north-eastern), respectively, from the 1930s to the 2000s. In Poland, some populations of A. bruennichi were expected to be more genetically isolated from others, due to distance effects or differential times of arrival. We evaluated whether the oldest populations were in a state of Hardy-Weinberg equilibrium (HWE), and whether recently founded populations were in an expansion phase. Specimens of A. bruennichi (n = 184) were collected at six localities in Poland and single sampling sites in Italy and Japan. Nine microsatellite loci were amplified although only five were useful in the final analyses. Based on the genotypes obtained, we estimated basic measures of genetic diversity and tested for deviation from HWE. The results showed a low level of polymorphism amongst the investigated markers, and accordingly, we found a low genetic diversity in populations. Only populations from Italy and Japan, and one population from Poland, were in HWE. The level of genetic differentiation among sampling sites from Poland was also very low. The high dispersal ability of the wasp spider appears to have facilitated high gene flow among populations. The peripheral and recently settled populations were characterized by the highest heterozygosity and the lowest inbreeding coefficient (F_IS)_. The remaining Polish populations are therefore still in the expansion phase, as indicated by deviations from HWE.

Fragmented remains of pseudoscorpions belonging to the family Cheiridiidae (Arachnida, Pseudoscorpiones) were recovered from Ychsma polity (c. AD 1000–1475) burial sediments from Pachacamac, Perú. Sediments from 21 burials were examined following rehydration in 0.5% trisodium phosphate for 48 h and subsequent screening through a 250 μm mesh. Materials larger than 250 μm were surveyed for the presence of arthropods. A total of two samples contained pseudoscorpion fragments, which were collected and quantified to determine the minimal number of pseudoscorpions present per gram of each sample. Following quantification, pseudoscorpion specimens were imaged utilizing confocal laser scanning microscopy (CLSM) to assist with identification efforts. Specimens have morphological characteristics consistent with those found in members of the pseudoscorpion family Cheiridiidae. Members of this family have not been previously described from archaeological materials recovered from Perú, and the implications of pseudoscorpions as members of the archaeological corpocenosis have not been fully interpreted. Herein, we report the first recovery of pseudoscorpions from archaeological materials at Pachacamac, and discuss the significance of their roles in the archaeological corpocenosis.

Three new hahniid species, Hahnia quadriseta sp. nov., Neoantistea multidentata sp. nov. and N. aspembira sp. nov., are described from a total of 1,131 individuals collected during spider inventories in Veracruz, Mexico. All specimens were collected inside four plots of Quercus forest, from leaf litter using active searching, sifted litter processed with Berlese funnels and pitfall traps. Sexual behavior and the natural history of N. aspembira sp. nov. are analyzed. In addition, the stridulatory organ morphology of both Neoantistea species is described. Stridulatory organs are absent in Hahnia quadriseta sp. nov., although present in other species of this genus. More information regarding this inventory and additional views of specimens can be found online at  http://www.unamfcaracnolab.com

The spiny trapdoor spiders (Idiopidae) of the Cataxia bolganupensis-group from south-western Australia are revised, and six species are recognized: C. barrettae sp. nov., C. bolganupensis (Main, 1985), C. colesi sp. nov., C. melindae sp. nov., C. sandsorum sp. nov. and C. stirlingi (Main, 1985). All species exhibit extreme short-range endemism, with allopatric sky-island distributions in mesic montane habitats of the Stirling Range, Porongurup Range and Mount Manypeaks. A molecular phylogenetic analysis of mitochondrial cytochrome c oxidase subunit I (CO1) and cytochrome b (CYB) sequences complements the morphological taxonomy, along with a key to species and detailed information on their distributions and habitat preferences. All six species are assessed as ‘endangered' using IUCN criteria, with the major threatening processes being the spread of the plant pathogenic fungus Phytophthora (causing dieback), climate change and inappropriate fire regimes.

The type species of the pseudoscorpion genus Geogarypus Chamberlin, 1930, Geogarypus minor (L. Koch, 1873), is redescribed from the newly designated female lectotype and numerous specimens from southern France, Corsica and Italy. Geogarypus nigrimanus (Simon, 1879) is newly designated as a junior subjective synonym of G. minor, and a new species, G. italicus sp. nov. (type locality Bergeggi, Western Liguria, Italy), is described from specimens from mainland Italy, Sicily and Sardinia. A key to the Mediterraneo-Macaronesian species of the genus is proposed.

Cohort splitting has been described as differences in time until maturation and / or life span in the same age group. Cohort splitting generally occurs when individuals of a cohort originating from the same season experience different environmental conditions, such as in early and late progenies. However, in the wolf spider Pardosa agrestis (Westring, 1861) spiderlings of the same clutch may follow either slow or rapid development, leading to a second adult peak within a year comprised of the rapidly developing individuals. We hypothesized that weather conditions experienced by the spiderlings in their early ontogeny may contribute to a life history decision between slow and rapid development. To test this hypothesis, we have used long term collection data and non-parametric habitat modeling. We found that highest abundance of the rapidly developing phenotype was correlated with a narrow range of early weather conditions. This result is in accordance with our early choice hypothesis, although the possibility remains that differential survival of the developmental morphs also contributes to the observed pattern.

Spider venom is assumed to be used primarily to subdue larger prey and secondarily in defense. Rabidosa rabida (Walckenaer, 1837) is a non-web building, venomous spider. Its feeding behaviors suggest venom may not be as important as previously expected in prey capture and immobilization. We conducted feeding tests to examine the importance of venom injection in prey capture for R. rabida. Groups of large crickets were offered to two groups of adult female spiders with either functional or glue blocked venom pores but otherwise functional chelicerae. Our results could not confirm a significant effect of venom availability on prey capture and showed that spiders could immobilize prey without the use of their venom. These results expand upon previous studies suggesting prey capture was possible without the use of the fangs, but prey immobilization required venom. This study suggests our understanding of spider prey capture and venom use is incomplete.