The first record of the palpigrade Eukoenenia gasparoi Condé 1988 in Croatia is reported. We review the distribution of this troglobiotic species endemic to the classical European Karst region, give an illustrated description of the adult stages and the juvenile female, and evaluate divergence among the populations. Morphological differences reflect individual-level rather than population-level variation.

Spelaeobochica iuiu sp. n. is described from Lapa do Baixão limestone cave in the municipality of Iuiu (Bahia, Brazil). It is easily distinguished from the two other species of the genus, S. allodentatus Mahnert 2001 and S. muchmorei Andrade & Mahnert 2003, by its pedipalpal measurements and proportions, but particularly by the presence of tooth-like protuberances on the pedipalpal segments. It is considered a troglobitic species.

Multivariate analyses of morphological characters provide strong evidence that a highland Vaejovis from the Sierra de los Ajos, a Madrean ‘sky island’ in northern Sonora, Mexico, represents a distinct new species of the V. vorhiesi group. This new species is described and compared to other geographically adjacent species of the V. vorhiesi group, named V. bandido, and brief notes on ecology are provided. Results from this study provide evidence that multivariate analysis of morphological characters is a powerful tool to delimit small and otherwise cryptic scorpion species.

A new species of Biantidae belonging to the genus Heterolacurbs Roewer 1912 is herein described. Heterolacurbs perezassoi new species from Puerto Rico, Greater Antilles, is the second species included in the genus, and it is clearly recognized by the pair of large spiniform apophyses on area IV that does not restrain area III of the dorsal scutum, the smooth legs, femora II–IV without dorsodistal spine, its tarsal formula, sternites with small tubercles and penis that exhibits a distinctive morphology.

Even though Hadrobunus grandis (Say 1821) is the type species of Hadrobunus, its identity has been uncertain since its original description. The type specimens were collected in coastal Georgia and/or northeastern Florida during the winter of 1817–1818, not from the mid-Atlantic Region (e.g.,Virginia, Maryland) as assumed by some authors. This error has resulted in persistent confusion with H. maculosus (Wood 1868), the dominant Hadrobunus species in the mid-Atlantic region. The type specimens of H. grandis were lost or destroyed, but all surviving evidence suggests that the species known as Leiobunum aurugineum Crosby & Bishop 1924 is a synonym of H. grandis. Examination of available museum specimens revealed two species. Populations east of the Apalachicola River correspond to the historical description of L. aurugineum in having sacculate penes, and are thus identical to H. grandis; those west of the river lack penial sacs and are placed in the new species H. nonsacculatus.

Relatively little is known about factors that contribute to microhabitat selection among Central American harvestmen. In this study, we compared walking and climbing speeds for five common species from Costa Rica representing the families Cosmetidae (3 species), Gonyleptidae (1 species) and Sclerosomatidae (1 species). Our sample included two arboreal species, two species that infrequently occupy perches in the vegetation, and one species that rarely climbs. Our analyses revealed no significant interspecific differences in climbing speed, although species with relatively long legs walked significantly faster than species with shorter legs. An arboreal habit did not correlate with increased climbing speed, and all species walked significantly faster than they climbed.

Recent studies of nutrient additions to terrestrial ecosystems have focused on the “aerial” portion of the food web associated with living plants. These studies showed nutrient loading increased arthropod abundance and biomass, but decreased diversity. However, none of these studies explicitly examined nutrient loading effects on epigeal arthropods. To test nutrient loading effects on epigeal spiders and on individual species within a temperate-latitude grassland community, we used pitfall traps to sample spiders for four years within 24 large (314 m²) plots in which we manipulated nutrients (NPK fertilizer) and plant litter (litter removed or left in place). We measured the diversity, abundance, biomass, and community structure responses of the spider community, and of wolf spiders (Lycosidae) and linyphiid spiders (Linyphiidae), as well as the abundance and biomass responses of the six most common species. We hypothesized increased nutrient loading would increase epigeal spider abundance and biomass but decrease diversity. Contrary to predictions, spider species richness, diversity, and biomass were not significantly affected by fertilization, while fertilization resulted in significantly increased abundance. Also contrary to predictions, plant litter did not affect any of these variables. Linyphiid spiders had the strongest responses to fertilization, with significantly increased abundance and biomass, and, contrary to predictions, increased species richness in fertilized plots. Wolf spiders responded more closely to predictions. Our results indicate that the epigeal spider community does not respond as would be predicted by biodiversity-productivity theory. This underscores the need to integrate the largely detritus-based epigeal community into current biodiversity-productivity theory.

Subsocial spiders are located on the continuum between solitary species and social species and are characterized by extended maternal care, some cooperation in foraging and colony activities and dispersal in order to found new colonies. In the genus Anelosimus (Araneae: Theridiidae), up to nine species are thought to be subsocial. One of these spiders, A. baeza Agnarsson (2006), is distributed across a large geographical range from Mexico to southern Brazil, and potential differences in behavior in different populations are unknown. We studied the ecology and behavior of a population of A. baeza in a cloud forest habitat in Mexico. We tracked the population for ten months, analyzed the degree of cooperation and the presence of associated species, and explored the settling decisions made by dispersing spiders. We show that the breeding season for A. baeza in Mexico differs from other populations elsewhere in South America. Using a kinematic diagram, we recorded the sequence of behaviors involved in subduing and feeding on a model prey species. Larger colonies harbored more associated species. Anelosimus baeza prefers to settle in locations that already contain conspecifics or silk. Our study demonstrates that A. baeza is a viable candidate for research into sociality in spiders and its geographical correlates.

Spitting spiders (Scytodidae) have a distinct predatory strategy in which they eject a sticky secretion from their cheliceral fangs to immobilize prey. This behavior could potentially allow the spider not only to avoid defensive secretions but also to bite specific vulnerable spots of a potential prey such as a harvestman. We used an ethogram, a fluxogram and an experiment to analyze the interaction between the harvestman Discocyrtus invalidus Piza 1938 (Arachnida: Opiliones) and the syntopic spider Scytodes globula (Nicolet 1849) (Arachnida: Araneae). These spiders, while readily taking crickets as prey, seldom spat at and never bit the harvestmen, which apparently did not exude repugnatorial secretions. We therefore tested, by clogging the glands and using appropriate controls, whether non-visible amounts of secretions could cause the rejection, but the harvestmen were still refused. This is the first detailed and quantified description of an interaction between a spitting spider and a harvestman. The general conclusions are that S. globula avoids preying on D. invalidus, S. globula behaves differently when attacking harvestmen and crickets and the scent gland secretions of D. invalidus do not play a direct role in this predator-prey interaction.

Animal body traits are scaled relative to overall body size depending on the evolutionary context. Most naturally selected traits are scaled approximately isometrically (constitute a constant proportion of the body size at different body sizes), whereas those under sexual selection tend to present positive static allometry (be proportionally larger in larger individuals). However, there are body traits that might be influenced by both natural and sexual selection. We studied the courtship behavior of the scorpion Centruroides margaritatus (Gervais 1841) and analyzed the static allometry of several body traits. We hypothesized that those traits that were actively used in courtship and seemed to be sexually dimorphic could be under sexual selection. The main sexually dimorphic traits were body size (female larger) and metasoma length (male longer). Although metasoma length of males had a steeper allometric slope (larger males had longer metasoma) than that of females, the slopes did not differ significantly. All body traits measured showed isometry with body size, except that the pecten presented negative allometry in males. Thus the length of the metasoma of males, thought to be influenced by sexual rather than natural selection, did not present positive allometry as expected. Males used the metasoma actively while courting females.

Nephila are known for the greatest degrees of sexual size dimorphism among orb weaving spiders (Araneoidea) and thus among terrestrial animals. However, a meaningful quantification of the dimorphism is lacking and the proximate developmental mechanisms of female gigantism are poorly understood, being attributed solely to female delayed maturation. Here we show that females in the giant wood spider Nephila pilipes (Fabricius 1793) become giants through facultative post-maturity molting, a phenomenon resulting in female carapaces on average 4.27 times longer than males' (ranging from 3 to 6.4 times), and female mass averaging 125 times the male's (ranging from 28 to 502 times). Although the small males follow a typical developmental pathway and reach maturity with their final molt, the females mature at varying sizes and instars and then continue to grow by molting the entire exoskeleton except their genitals. The newly discovered phenomenon of additional, single-sex, adult, non-genital molting may represent a critical developmental adaptation that facilitates female gigantism in Nephila as a response to fecundity selection.

Parasitoids can have significant impacts on the life history of their hosts, as well as on local population and community dynamics. These effects could be particularly pronounced in the Arctic where the breeding season is short. We studied the incidence and loads of egg sac parasitoids, and whether these varied with body size or among species in three Arctic wolf spider species: Pardosa sodalis Holm 1970, Pardosa lapponica (Thorell 1872) and Pardosa moesta Banks 1892 from the Yukon Territory in northwestern Canada. We found a high incidence of egg sac parasitism (by Gelis sp.) and that the incidence of parasitism increased significantly with body size in two of the spider species; however, it did not change in the largest species. Among the three species investigated, parasitism was highest in the largest species (P. sodalis). Parasitism loads ranged from one to fourteen individuals per egg sac, and incidence reached 29.6% overall in P. sodalis. Parasitism may have significant impacts on the life history of tundra wolf spiders.