In web-building spiders, females are often too widely distributed across the landscape for males to monopolize more than one mate. Consequently, males seek females one at a time and may cohabit with females in their webs. Pre-copulatory cohabitation is most common in araneomorphs, which suggests that the first male to mate with a female will have a greater share of paternity than any subsequent mates (first sperm precedence). However, pairs of adult New Zealand sheet-web spiders (Cambridgea foliata (L. Koch, 1872); Desidae) cohabit for longer than required to achieve copulation. This is counter-intuitive as it suggests that males defend females they have already copulated with, in lieu of seeking additional mating opportunities. To investigate the costs and benefits of extended cohabitation on male and female C. foliata, we conducted surveys of webs of solitary and paired males and females. We found that solitary spiders of both sexes consistently position themselves in the center of their webs but that when in pairs, females are displaced from the webs by males and will frequently leave the web altogether. Males in pairs would respond to vibrations simulating prey, while females would not respond. This strongly suggests that extended cohabitation should be costly for females. By contrast, for males, cohabitation is a valuable foraging strategy which, combined with the advantages of mate-guarding, may compensate for any lost mating opportunities due to foregoing searching for further mates.

Jumping spiders perform multi-modal displays during courtship and this has been used to study sexual selection and mate choice. However, studies have focused on only a few groups of spiders. Here we describe for the first time the breeding behavior of the tropical jumping spider Hasarius adansoni (Audouin, 1826). Animals were collected in the field and reared in the laboratory until adulthood. We took male body measurements, paired couples in mating trials, and then collected subsequent clutches. We confirmed the presence of a multi-modal display with visual and vibratory signals (tremulations) by the males. Females responded with their own tremulations and occasionally a receptive posture. Otherwise, they avoid mating by attacking or running away from the male. No measured male morphological attributes were important for male mating success and future studies should focus on other morphological measurements to understand how the mate choice process functions in this species. Multiple matings were common and females laid numerous clutches while enclosed in silk cocoons. Number of young per clutch decreased over the course of laying bouts.

Nuptial feeding has variable effects on fitness within a species, partly driven by variation in female diet. We investigate nuptial feeding in the spider Pisaura mirabilis (Clerck, 1757) under a feeding regime that has not been explored: starvation after mating and gift consumption. We vary gift size and gift number to examine the effects on mating behavior and components of female fitness. With regard to gift size, copulation duration increased with larger gift size, but no component of female fitness was affected (time to oviposition, egg sac mass, female lifespan). These results corroborate other examinations of gift size in P. mirabilis. Given a likely male benefit (prolonged copulation) for larger gift size and no demonstrated female benefit, sexual conflict stands as a likely explanation for male benefits due to large nuptial gift size. With regard to gift number, components of female fitness were not affected by the consumption of one or two extra gifts. This agrees with other studies, although we note that some experiments have found the consumption of extra gifts to increase female fitness. As for males, they were more likely to copulate when they had gifts, as in other studies. We conclude some support for sexual congruence with regard to gift number, as males and females stand to benefit simultaneously from the mere presence of the gift, and females might benefit from the consumption of multiple gifts. Thus, both sexual conflict and sexual congruence appear to be at work regarding the evolution of nuptial gifts in Pisaura mirabilis.

There is a need for reliable and standardized methods to measure functional species traits. Body mass is just one dimension of body size, a most important morphological trait, because it is directly linked with metabolic rate and affected by environmental conditions. However, it is still not widely used due to the difficulties and constraints of direct measures. Weighing many (small) animals (i.e., arthropods) is laborious, time consuming and biased when using preserved material. Therefore, the applicability of general equations for estimating mass from body size of spiders was tested. We calculated linear regressions to estimate fresh and dry mass of spiders from different body measures (i.e., body length, carapace length and width) of 189 spiders sampled in southern Germany. We compared these regressions with each other and with equations from the literature and tested the impact of taxa, sex and habitat on the accuracy of biomass estimates using an independent test dataset of 166 spiders. All size-fresh mass regressions were highly significant with R² values between 0.81 and 0.98. The slope of the ln-transformed body mass - body size relationship ranged between 2.51 and 2.95. The regressions including total body length always showed higher R² values, i.e., they provide better predictions of body mass than carapace measures. The body length-dry mass regression was also highly significant and the mean ratio dry mass/fresh mass was 0.22. Taxon-, sex- or microhabitat-specific regressions did not produce better estimates than general regressions. Therefore, we strongly recommend the use of general regressions in the context of biomass estimation of assemblages and propose parameters from our regressions to be used for European spiders.

We conducted a two-year mark-recapture study of a synanthropic population of the brown recluse spider Loxosceles reclusa Gertsch & Mulaik, 1940 in northwestern Illinois. We used joint live encounter and dead recovery models to estimate adult survival, recapture, and dead recovery probabilities. To estimate adult abundance, we used full-likelihood closed-population models. Monthly survival was constant between sexes (0.73, 95% CI = 0.66–0.78), but males were less likely to be recaptured and an additive effect of time revealed highest recapture probabilities in September. The probability of recovering a marked adult that died during the study was 0.13 (95% CI = 0.07–0.24). Average life expectancy for adults was 94 days, much lower than in prior laboratory studies. Causes of observed mortality were predation by conspecifics and cobweb spiders (Parasteatoda tepidariorum (C.L. Koch, 1841)) or undetermined. A likely source of mortality for this sit-and-wait predator is starvation. Model averaging of full likelihood closed-population models resulted in adult abundance estimates that were similar between males (28, 95% CI = 20–63) and females (28, 95% CI = 26–38). However, the total population of adults including those hidden in harborage (boxes, furniture, crevices etc.) was undoubtedly much higher. Based on count data, immature spiders were as abundant as adults early in the year, gradually increasing to a peak three times greater by mid-summer. Male spiders moved longer distances than females and were less likely to exhibit site fidelity. The average tenure of a female at a specific site was nearly 8 days.

Habitat associations of two species of congeneric web-building wolf spiders were examined in their zone of syntopy on the Lake Wales Ridge in Florida. The species differed in use of all of the habitat variables measured. The geographically widespread species, Sosippus floridanus Simon, 1898, associated with habitat features typical of scrubby flatwoods and human disturbed areas, which are found throughout the Florida peninsula. The endemic species, S. placidus Brady, 1972, associated with a scrub oak habitat that is restricted to the Lake Wales Ridge. Biogeographic implications of these differences are discussed.

Scorpions fluoresce a bright green when under ultraviolet light, but the functional significance of the fluorescence is still unknown. A major challenge in studying scorpion fluorescence is the lack of efficient methods for testing the behavioral photosensitivity of scorpions. We have modified previous assays to produce a more sensitive testing device. The apparatus consists of a circular track made of a small Petri dish nested inside a larger one, with an LED shining from the inner chamber across a small sector of the track. We monitored the scorpions' movements in the arenas under three light wavelengths: ultraviolet (399 nm), yellow-green (566 nm), and red (630 nm); all wavelengths were matched to a nighttime light intensity (0.01 irradians). We also tracked each animal's movements in the absence of light as a control. The animals were attracted to 399 and 566 nm light and also showed some attraction to 630 nm. Furthermore, earlier studies suggest that scorpion photoreceptors form a homogeneous population that has been physiologically shown to be maximally sensitive to green wavelengths. We hypothesize that the photoreceptor population might be somewhat responsive to red light too, suggesting that the photoreceptors may respond to a broad spectrum of light or that the photoreceptor population may not be as homogeneous as previously thought. The strong response to UV light, as has been seen in other behavioral assays, remains enigmatic. Overall, this new assay is more sensitive than previous assays for detecting scorpion photoresponse and will be useful for future studies.

The aganippine spiny trapdoor spiders of the genus Gaius Rainbow, 1914 are revised. Seven new species are described from Western Australia: G. aurora sp. nov., G. austini sp. nov., G. cooperi sp. nov., G. hueyi sp. nov., G. humphreysi sp. nov., G. mainae sp. nov. and G. tealei sp. nov. The type species, G. villosus Rainbow, 1914, is re-illustrated and re-diagnosed, and molecular data for six (of eight) species and six genes are analyzed with Bayesian methods. Species of Gaius are iconic denizens of the Western Australian inland arid zone, renowned for their large size and extreme longevity. We here document the known diversity and conservation status of these spiders, and summarize their unusual biology and phenology.

We studied the male holotype of Cercophonius himalayensis Lourenço, 1996, the sole member of the scorpion family Bothriuridae from India, and concluded that it belongs to a species of the genus Phoniocercus Pocock, 1893, which is endemic to the temperate forests of Patagonia. The presence of a Patagonian genus in India is extremely unlikely; therefore, we consider this to be a case of mislabeling of the specimen, and consequently exclude the scorpion family Bothriuridae from Indian fauna. Cercophonius himalayensis is transferred to the genus Phoniocercus, and formally synonymized with Phoniocercus sanmartini Cekalovic, 1968. A brief illustrated description of the type specimen is made, emphasizing important diagnostic characters and some body parts not previously described, such as the hemispermatophore. We also present a probable explanation for the origin of the material.

Members of the Neobisiidae are currently classified in two subfamilies, Neobisiinae and Microcreagrinae. Taxonomic assignment to subfamily is based upon two morphological characters, neither of which is consistently found within either subfamily. The form of the galeae is elongate and hyaline in the Microcreagrinae, but reduced and sclerotic in the Neobisiinae. However, some members of the Microcreagrinae also have reduced galeae. The position of trichobothrium ist located on the fixed finger of the pedipalp chelae is generally positioned subdistally and closer to trichobothrium est in Neobisiinae but sub-basally and closer to trichobothrium ib in Microcreagrinae. However, members of the genus Parobisium, currently assigned to the subfamily Neobisiinae, have a microcreagrine-like subbasal trichobothrium ist. Since neither subfamily is defined by an undisputed apomorphy, the monophyly of both groups has long been questioned. In this study, we tested whether or not the two subfamilies are monophyletic by inferring the phylogeny of the family using DNA sequence data from the mitochondrial protein-coding gene, COI, and the nuclear ribosomal gene 28S. Results of the molecular phylogenetic analyses indicate that neither of the subfamilies is monophyletic as presently defined. We transfer the genus Parobisium to the Microcreagrinae in order to simultaneously obtain a monophyletic Neobisiinae and resolve character inconsistency for the position of trichobothrium ist, which is sub-distal in all Neobisiinae taxa included in our study. We also find that reduction of the galea is not a reliable character state at the subfamily level, and has occurred at least three times independently within the family.

The harvestman genus Propachylus Roewer, 1913 is herein revalidated from the synonymy of Discocyrtus Holmberg, 1878. Its type species, Propachylus singularis Roewer, 1913 has a convoluted taxonomic history, connected to Discocyrtus fornicatus Sørensen, 1884 (currently known as Metadiscocyrtus fornicatus). The monotypic genus Metadiscocyrtus Roewer, 1929 is herein considered a junior subjective synonym of Propachylus. Propachylus singularis (known only from males) is herein considered a junior subjective synonym of M. fornicatus (Sørensen, 1884) (known only from a single female). Accordingly, this species is herein newly combined as Propachylus fornicatus (Sørensen, 1884) comb. nov. The males and females of this species are considered congeneric for the first time. As this species does not possess diagnostic characteristics of the concept of Pachylinae stricto sensu, it is here removed from Pachylinae but is left unplaced. The geographical distribution of this species is updated to the Brazilian state of Bahia.

We present the first recorded description of females of the species Dinorhax rostrumpsittaci (Simon, 1877) from solifugae specimens obtained from southern Vietnam. As a result of DNA barcoding using males identified as D. rostrumpsittaci and unidentified females, these female specimens made a highly supported cluster with male D. rostrumpsittaci. Hereby, we describe the female D. rostrumpsittaci and its natural habitats.

The Australian schizomid fauna consists of eight genera distributed across the northern half of the country, and are mostly restricted to rainforest or subterranean ecosystems. Several schizomid species have been previously described from the arid Pilbara bioregion of Western Australia, occurring in subterranean cavities that are accessible only by troglofauna sampling. We document the schizomids from subterranean habitats on the western edge of the Hamersley Range using morphological characters and sequence data from the genes COI, ITS2 rRNA, 12S rRNA and 28S rRNA. Several genetic clades were found to cluster geographically, consistent with the geomorphology of the region. Adult males were available for four clades (Paradraculoides affinis sp. nov., P. cochranus sp. nov., P. confusus sp. nov. and P. trinity sp. nov.), females only were present for two clades (P. catho sp. nov. and P. obrutus sp. nov.), and only a single juvenile was available for another clade (P. celatus sp. nov.). We hypothesize that each of these clades represent distinct species which are here named and described.

The characteristics and designs of webs provide valuable information on ecology, behavior and phylogenetic relationships. Characters are often obtained from detailed analyses of web photographs. We describe new methods to enhance web visibility; they consisted of painting the inner surfaces of Petri dishes with an opaque black spray paint that produced a rough surface, and then applying a salt spray from a nebulizer or fine white powder to tiny webs constructed in there. Using these methods on webs of Oecobius concinnus Simon, 1893, we discerned several unknown details of the refuge and cribellar threads that had previously gone undetected.

A survey of reports on spiders preying on small, non-flying mammals (i.e., mice, deer mice, voles, rats, heteromyid rodents, shrews) published in the literature and in the social media yielded a total of 42 naturally occurring incidents. Spiders from five families (Agelenidae, Ctenidae, Sparassidae, Theraphosidae, and Theridiidae) were reported capturing small mammals under natural conditions. Additionally, spiders from four more families (Atracidae, Lycosidae, Pisauridae, and Porrhothelidae) are known to kill small mammals in captivity. Approximately 80% of the reported incidents were attributable to theridiid spiders, especially the Australian redback spider (Latrodectus hasselti Thorell, 1870) and three species of North American widow spiders (Latrodectus geometricus C.L. Koch, 1841, Latrodectus hesperus Chamberlin & Ivie, 1935, and Latrodectus mactans (Fabricius, 1775)) that have been shown to be expert mouse-catchers. The success of widow spiders in subduing small mammals can be explained by their ability to spin strong webs made up of tough silk, and producing a very potent toxin (α-latrotoxin) specifically targeting the vertebrate nervous system.

Species differ in their reproductive abilities, which may affect their success. In southwest Ohio, populations of Pholcus phalangioides (Fuesslin, 1775) (Araneae: Pholcidae) have largely been replaced by Pholcus manueli Gertsch, 1937 (Araneae: Pholcidae). We suspected that differences in reproductive output underpinned the success of P. manueli. We documented the reproductive success of both species in the laboratory. Female P. phalangioides mated more readily and were more likely to produce eggsacs than P. manueli, but the timing of eggsac production and spiderling emergence were similar. The eggsacs of P. phalangioides contained smaller numbers of larger eggs but similar numbers of spiderlings emerged from the sacs of both species. We uncovered a negative relationship between egg size and number for P. phalangioides, but not for P. manueli. Our results do not explain the relative success of P. manueli, however, we have uncovered differences in the reproductive strategies utilized by these ecologically-similar congeners.

Little is known about reproduction in most cave spiders, including reproductive behaviors, seasonality, and fecundity. In the course of fieldwork in Tennessee caves, we observed aspects of reproduction in three populations of Liocranoides Keyserling, 1881 (Araneae: Zoropsidae) spiders. We observed egg sacs of L. archeri Platnick, 1999, as well as egg sacs and spiderlings of L. cf. gertschi Platnick, 1999. The spiders produced a spherical egg sac that hung from the cave ceiling by a single cord of silk. The egg sacs were covered by foreign material including sediment, rocks, and plant roots. Egg sacs were observed in June and July, and spiderlings were observed in July. Three egg sacs that were collected contained 26, 42, and 53 eggs. This is the first description of reproduction in Liocranoides.