The Caribbean Islands are a biodiversity hotspot harboring high levels of endemic biodiversity. In an effort to contribute to the characterization of invertebrate diversity in the region, we present an assessment of pseudoscorpion (Arachnida: Pseudoscorpiones) diversity and distribution with a focus on the superfamily Chthonioidea and the family Olpiidae. We used three markers (cytochrome c oxidase subunit I, histone H3 and 28S rRNA) to infer the first molecular phylogenies for each lineage and identified 32 putative new species in need of taxonomic assessment. These new records include the documentation of the genera Pseudochthonius Balzan, 1892 Lagynochthonius Beier, 1951, Tyrannochthonius Chamberlin, 1929 (Chthoniidae), Antillolpium Muchmore, 1991, Novohorus Hoff, 1945, and Pachyolpium Beier, 1931 (Olpiidae) on various islands. Chthonioid genera are strongly structured geographically, suggesting that many Caribbean species may be short-range endemics and excellent candidate systems for testing biogeographic hypotheses. The olpiid genus Pachyolpium is less geographically structured, which is consistent with the hypothesis that olpiids are better dispersers than chthonioids. This study aims to provide a foundation for taxonomic and biogeographic work on Caribbean pseudoscorpions, revealing a diversity that is far richer than is documented in the literature.

A review of the pseudoscorpion family Ideoroncidae in the Asian region reveals three genera: Dhanus Chamberlin, 1930, Shravana Chamberlin, 1930 and a new genus. Dhanus includes four species, D. sumatranus (Redikorzev, 1922), D. hashimi sp. nov. and D. tioman sp. nov. from Malaysia, and D. lunaris sp. nov. from Cambodia. Dhanus doveri Bristowe, 1952 is newly synonymized with D. sumatranus, and the type locality of D. sumatranus is confirmed as the Dark Cave, in the Batu Cave system, near Kuala Lumpur. Shravana is confirmed as a senior synonym of Nhatrangia Redikorzev, 1938 and includes 13 species: S. laminata (With, 1906) and S. schwendingeri sp. nov., from Thailand, S. charas sp. nov. and S. withi sp. nov. from Malaysia, S. dawydoffi (Redikorzev, 1938), comb. nov. (transferred from Nhatrangia) from Cambodia, Laos, Vietnam and the Spratly Islands, S. indica (Murthy & Ananthakrishnan, 1977), comb. nov. (transferred from Dhanus) from India, S. ceylonensis (Mahnert, 1984), comb. nov. (transferred from Nhatrangia) from Sri Lanka, S. afghanica (Beier, 1959), comb. nov. (transferred from Dhanus) and S. magnifica sp. nov. from Afghanistan, S. latens sp. nov. from Iran, and S. pohli (Mahnert, 2007), comb. nov. (transferred from Dhanus), S. socotraensis (Mahnert, 2007), comb. nov. (transferred from Dhanus), and S. taitii (Mahnert, 2007), comb. nov. (transferred from Dhanus) from Socotra. A new genus, Sironcus, is described for the type species Ideobisium (Ideoroncus) siamensis With, 1906 from Thailand and five new species, S. rhiodontus sp. nov. and S. stonei sp. nov. from Thailand, S. sierwaldae sp. nov. from Thailand and Myanmar, S. jerai sp. nov. from northern peninsular Malaysia and S. belaga sp. nov. from Sarawak.

The postembryonic development of Opiliones (Arachnida) includes three phases: larval, nymphal (with four to eight instars), and adult (when molts cease). The present study aimed to describe the postembryonic development of Heteromitobates albiscriptus (Mello-Leitão, 1932) (Gonyleptidae) including both a morphometric study and SEM analysis of two structures present in the tarsus of nymphs and adults: the “tarsal aggregate pores” (TAPs) and the “tarsal perforated organ” (TPO). The nymphal phase includes five stages, which can be easily recognized by morphometric values. In contrast to the pectinate tarsal claws found in legs III–IV of adults (the main synapomorphy of the genus Heteromitobates in the subfamily Goniosomatinae), nymphs bear smooth claws. First nymphs lack TAPs and TPOs. TAPs seem to have a precisely defined position in both prolateral and retrolateral faces of the tarsus. The number of pores in TAPs grows from three or four among second nymphs to around 20 among adults, and measure around 2.15 μm in diameter with no clear difference between ages. An additional field of pores on legs III–IV (“ventral tarsal aggregate pores”, vTAPs) was detected only among adults. The plates at the base and the apex of the TPOs differ from the ones in between. The length of the TPO and its number of plates increase with each molt. However, there is no discernible pattern of growth throughout the postembryonic development when taking into account both the average size of the plates (ranging between ∼7–11 μm) and the ratio of TPO length to tarsus length.

Spiders can suppress populations of some important crop pests. Although dispersal is essential to their survival in the disturbed farmland environment, accounts of their dispersal activity over several seasons are few. Spiders dispersing across a landscape of mixed farmland were sampled over an 18-month period using Stick, Net and Bottle traps (SNB traps). Traps were located in a two year old grass ley where ground densities of spiders and wind speed data were also recorded. SNB traps were effective at sampling large numbers of dispersers; Linyphiidae were the most abundant family sampled (93%). Numbers of adult linyphiids dispersing were found to increase in autumn and winter with dispersal activity occurring frequently throughout the study period. Dispersal patterns were similar for congeners (Erigone spp., Oedothorax spp.) although differences were evident between common agrobiont species. Weather conditions associated with stable high-pressure systems appeared important for stimulating mass dispersal in Oedothorax Bertkau, 1883 species. Erigone atra Blackwall, 1833 dispersed more frequently and under more variable conditions. Winter and spring dispersal was low for adult Tenuiphantes tenuis (Blackwall, 1852) and Bathyphantes gracilis (Blackwall, 1841) compared to common erigonids. Ground populations correlated positively with dispersing spiders for some species indicating that dispersal activity was in part a function of population size. For Oedothorax fuscus (Blackwall, 1834) it is suggested that life history traits and weather conditions may interact to influence the sex ratio of dispersers over time.

Spiders are a diverse and abundant group of predaceous arthropods in arid environments. Spiders in the genus Eresus Walckenaer, 1805 are widely distributed in mesic and arid regions of the Palaearctic, but data on their diet are scarce. The goal of this study was to analyze the diet of Eresus kollari Rossi, 1846 in an arid habitat of the southeastern Iberian Peninsula. A total of 64 webs of Eresus kollari with prey remnants were collected in a field site at the Guadix-Baza Basin, and prey were identified to species or the lowest possible taxonomic level, and counted. Prey size was estimated based on remains from the webs and voucher specimens from the study area. In addition, laboratory observations of prey capture were made. The results showed that E. kollari has a broad diet, including prey from a total of 106 taxa. Prey included large arthropods (mostly tenebrionids) as well as relatively small insects (e.g., ants, which constituted a high proportion of prey). Laboratory observations showed that adult E. kollari actively captured tenebrionid beetles crawling on silk threads around the web, and ants moving on the surface of the web sheets. The high proportion of large-size prey in the webs studied, especially tenebrionids, indicate that this spider has a diet similar to that of Latrodectus lilianae Melic, 2000 in the study area, but the different hunting techniques used by the two spiders probably account for the dissimilar proportion of ants and predacious arthropods in the two diets.

The phylogeographic structure of some species distributed across the Baja California Peninsula has been traditionally hypothesized as resulting from vicariant events thought to have occurred between 1–3 Mya. Climatic fluctuations during the Pleistocene have also been shown to influence the distribution patterns of species, and vicariant patterns may have been erased as a consequence of population contractions or expansions into or out of refugia generated during the last glacial maximum ca. 21,000 years ago. Thus, there is still some uncertainty regarding the relative role of vicariance in shaping the modern biota of Baja California. To understand the evolutionary history of the wolf spider Pardosa sierra Banks, 1898 on the peninsula, a phylogeny of this species and closely related taxa was generated using a fragment of the mitochondrial gene cytochrome c oxidase subunit I (CO1). Sequences of a fragment of the CO1 gene for 38 individuals from 14 sampling sites along the entire distribution range of P. sierra were used to infer phylogeographic patterns, and five nuclear microsatellite loci were also used to genotype 296 individuals from seven of these 14 locations. The current and past potential distributions from two Pleistocene periods were estimated using niche-based distribution modeling, and scenarios of colonization from detected refugia were simulated. We found that Californian populations of P. sierra diverged from peninsular populations 4 Mya, this divergence coinciding with the northern-gulf split. However, we did not detect genetic breaks in regions where the mid-peninsular and Isthmus of La Paz canals were presumably formed, either with mitochondrial DNA sequences or microsatellite loci. Two refugia were further detected at the geographic ends of the peninsula, these likely preceding subsequent habitat expansion.

Alternative mating tactics are often expressed differentially based on a variety of factors associated with each mating context in order to maximize a male's reproductive success. In particular, males of many species attempt to reduce competition with males in the surrounding environment by altering their mating behaviors. In the wolf spider Rabidosa punctulata (Hentz, 1844), males exhibit two distinct mating tactics: 1) courtship—comprised of visual and seismic signals or 2) direct mount—involving males grappling with females for copulation. In natural environments, these spiders are relatively dense. Competing males are often close by and could potentially intercept courtship displays, locate the nearby female and steal the copulation. Here we investigate whether males adjust their mating tactic expression in response to indirect and directly competing males, and whether these decisions affect their likelihood to copulate. In both experiments, the actions of a competing male did not affect the expression of any male mating behaviors in the other, suggesting a lack of an effect of scramble competition on tactic expression. Evidence from our triad mating experiment suggests a mating advantage for males that adopt the direct mount tactic when in direct competition with other males. In particular, direct mounts were most successful when multiple males were actively pursuing a female and when adopted first among the competitors. Additionally, we observed direct male mating interference whereby the copulating pair was broken up. Following these breakups, females were observed to mate multiply, often as a result of a direct mount. This new observation may provide a context in which males benefit through additional copulations by adopting the direct mount tactic.

A major advantage of having behavior controlled by a circadian clock is that the organism may be able to anticipate, rather than respond to, important daily events in its environment. Here, we describe the behavioral rhythms of locomotor activity and web building in the orb-weaving spider Cyclosa turbinata (Walckenaer, 1841). Web building occurs late in the scotophase, in absolute darkness, and is initiated and completed before lights-on under light:dark cycles in the laboratory. This scheduling presumably enables web-building to occur under the cover of darkness, thereby avoiding visual predators. Locomotor activity occurs predominantly in the dark with a sharp peak within one hour after lights-off and a broader peak occurring before lights-on. The locomotor activity rhythm free runs under constant dark and constant temperature conditions, thus indicating endogenous circadian control. Evidence from the free running rhythm suggests that the first peak under light:dark cycles is a result of masking but that the second peak is attributable to the endogenous circadian oscillator. The period of the free run is exceptionally short, about 19 hours. In comparison with locomotor activity, web building is quite sporadic under constant dark conditions, making detection of periodicities difficult and, therefore, whether web-building is under endogenous circadian control or is driven by exogenous factors remains unresolved.

Leaf masquerade—an animal resembling leaves that are inedible for predators or innocuous for prey—is well known in insects but less so in arachnids. We report a case of a striking morphological and behavioral adaptation that can be labeled as leaf masquerade in an undescribed spider species (Poltys C.L. Koch, 1843, Araneidae) from southwest China. The female abdomen has anatomical analogues of a leaf pedicel and venation, and its color is both green and brown, thus resembling both live and dry leaves. The spider camouflages itself with pulled dead leaves among live ones. This novel natural history in a spider adds an arachnid model to the growing literature on animal masquerade.

We compared the effect of Ultraviolet A radiation on the adhesive droplets of the diurnal orb-web weaver Argiope trifasciata Forskaal, 1775 and the nocturnal orb-web weaver Neoscona crucifera (Lucas, 1838). We hypothesized that glycoprotein glue within A. trifasciata droplets will either be unaffected or will benefit from UVA exposure, whereas the glycoprotein of N. crucifera will be degraded by UVA. In both species, the volume of fresh droplets did not differ from that of droplets that were exposed to UVA for four hours, or from the volume of droplets kept in the dark for four hours. This documented that UVA did not affect compounds that confer droplet hygroscopicity. Both dark and UVA treatments reduced the relative toughness of droplet glycoprotein, though the reductions were not statistically significant, with the dark treatment exhibiting a greater decrease in relative toughness. This study suggests that ecologically relevant levels of UVA exposure do not affect the glycoprotein glue of orb-weaver capture silk.

Two species of common, farmland-inhabiting money/dwarf spider, Erigone atra Blackwall, 1833 and Oedothorax fuscus (Blackwall, 1834), were exposed to light wind conditions within a wind chamber to determine their propensity to exhibit dispersal behaviors over a nine-month period. A novel design of wind chamber, incorporating two tangential fans, produced a wide outflow thereby allowing behaviors to be expressed over a relatively large test area (1 m × 0.65 m). Sticks placed at 3 cm intervals in an undulating foam surface structurally mimicked a natural field setting. Whereas the majority of E. atra expressed dispersal and related behaviors (tiptoe and drop posture and ballooning) in every month testing occurred, corresponding behaviors were rarely recorded in O. fuscus. Results are discussed in relation to knowledge of the dispersal activity of O. fuscus in the field and factors which may influence dispersal frequency and initiation.

The physiological effects of resource allocation due to dietary restriction in spiders are poorly understood; in fact, the system-wide effects of any environmental stresses on spider physiology remain relatively unstudied. The aim of this study was to show the consequences of dietary restriction in the pholcid spider Physocyclus mexicanus Banks, 1898. Male spiders were fed either a high (ad libitum) diet (n = 43) or low (5–8 Drosophila melanogaster/week) diet (n = 32) through their penultimate instar. We found significant differences in testis volume, body mass, and tibia-patella length [TPL] between the two groups. Linear regression analysis reveals that the differences in testis volume between the two groups are not solely due to differences in body mass; for any given body mass, the low diet group has a smaller mean testis size than the high diet group. Our results suggest that P. mexicanus males allocate resources away from testis volume in times of scarcity.

We describe for the first time the sexual behavior of Pavocosa gallopavo (Mello-Leitão, 1941) (Lycosidae), analyzing encounters between 25 pairs of virgin adult individuals. Both courtship and copulation were brief, averaging 3.66 min and 1.74 min respectively. Males showed a very conspicuous and vigorous courtship, with Leg Shaking and Palpal Drumming as the most noticeable displays. Females were also active during courtship, performing Leg Waving as well as showing some level of aggression by displaying Cheliceral Opening and Pushes against males. The males mounted the females in the typical position of wolf spiders, and females initially performed intense body shakes (Bucking). The copulatory pattern consisted of alternating single insertions of both palps, with a unique hematodochal expansion by insertion. Females cannibalized males three times, two of them before copulation and the third after copulation. Copulation was brief with respect to other wolf spiders, and females were unusually active during copulation. The species would be suitable for further studies of multimodal communication and the sexual inhibition of female aggression.