Arachnologists have uncovered tantalizing details about amblypygid behavioral ecology—the study of the fitness consequences of their behavior. Thus, it is the aim of this review to position Amblypygi as a useful system in which to investigate the principles of animal behavioral ecology. We synthesize amblypygid habitat preference and navigation modalities; predator, prey, parasite, parasitoid, cannibal, and commensal interactions; resource contests and territoriality; mating systems and mate choice; parental investment and sociality; and genetics and genomics as they relate to behavioral ecology. We present ideas for future research in each of these areas and discuss future directions for Amblypygi behavioral ecology research as they relate to four areas of behavioral ecology: adaptation, evolutionary history, mechano-sensory control of behavior, and behavioral development. We conclude by identifying several avenues of Amblypygi behavioral ecology that we think have the highest potential for transformative discoveries.

Spiders, a group of predominantly insectivorous predators, occasionally use plant food to supplement their insect prey. In the current review, we tracked down 95 reported incidents of spiders feeding on plant food under natural conditions. Globally, >60 spider species representing ten families have been observed feeding on plant materials from over 20 plant families. Cursorial spiders including the families Anyphaenidae, Clubionidae, Eutichuridae, Salticidae, Thomisidae, and Trachelidae dominate among the spiders feeding on plant food (>80% of reported incidents). Spiders feed on a wide diversity of plant-derived products including floral nectar, extrafloral nectar, stigmatic exudate, plant sap, honeydew, seeds, Beltian bodies, Müllerian bodies and pollen (originating from very different plant types such as coniferous and deciduous trees, herbaceous plants and shrubs, annual weeds, grasses, climbing plants, orchids, carnivorous plants, and ferns). Furthermore, spiders have been shown to consume fungal spores in laboratory trials. Supplementary feeding on plant materials by spiders was shown to be global in extent and widespread across spider taxa, plant taxa and plant materials; however, the extent to which the different categories of plant food contribute to the spiders’ diet and how this may affect their behavior and life history is still largely unexplored. This review is expected to lay a foundation for future research on this topic.

Spatial and temporal heterogeneity of suitable habitat in grasslands can promote species and functional diversity in arthropods, including responses by ubiquitous web-building spiders. A field experiment in tallgrass prairie habitat was performed to examine the response in abundance and web-type richness of aerial web-building spiders to changes in the availability of structure for web placement (vegetation architecture). To test the hypothesis that vegetation structure contributes directly to the web-builder abundance and web-type richness in open grasslands, we increased vegetation structure by adding dead woody stems of a common shrub along transects in each of three watersheds that differed in burn histories and existing habitat structure. Aerial web-building spiders were visually censused before and after the manipulations, at which time we recorded web-orientation, height, web-type, and the presence/absence of the spider associated with a web. Over the duration of the study, a total of seven web-type groups were encountered, of which medium-sized orb weavers were the most abundant web-building group across all watersheds. In general, higher spider abundances of orb-building spiders were observed in sections with added structure compared to the non-manipulated sections. However, reduced richness of web types was found on the manipulated sections of transects, suggesting that the architecture provided by woody stems does not provide sufficient and appropriate web-anchoring structure for the full range of web-building spiders groups in tallgrass prairie.

Fragmentation of natural habitats is considered one of the greatest threats to the maintenance of global biodiversity. In this study, we tested the importance of forest patch size and vegetation structure on the richness, diversity, abundance, and composition of the orb-weaving spider guild in an area of the Atlantic Forest (State of São Paulo, Brazil). We sampled 16 sites, grouped into the following categories composed of four sites each: continuous mature forest, continuous secondary forest, large (52–175 ha) secondary forest fragments, and small secondary forest fragments (14–28 ha). The richness ranged from 29 to 55 species per site, but was unrelated to forest size or vegetation structure. The communities from the continuous mature forests were more abundant and less diverse than those from the other categories, but this was due to a few dominant species. The changes in composition were related to the vegetation structure, suggesting that this variable is more important to the composition of orb-weaving communities than the size of the forest patch. Overall, the results indicate that the orb-weaving spider community in this region, even in the fragments, is still rich and diverse, which may be attributable to some characteristics of spiders, such as generalist behaviour and a good dispersal capacity. Nonetheless, our results also highlight the importance of continuous areas, especially those with mature vegetation that harbor a characteristic orb-weaving community that can serve as a source for the fragments.

Phylogenetic niche conservatism can cause strong interspecific competition among closely related species leading to competitive exclusion from local communities or meta-communities. However, the coexistence of close relatives is often reported. One of the most frequent mechanisms mediating such coexistence is resource partitioning. Here, we investigated the niche differentiation of two sibling spider species, Pardosa alacris C.L. Koch, 1833 and P. lugubris Walckenaer, 1802, along a canopy openness gradient. We further investigated differences in body size as an additional axis for niche partitioning. We explored niche partitioning along the canopy openness gradient at eight locations. In each afforested location, 60-m-long transects were established consisting of five pitfall traps placed at regular 15-m intervals along the gradient. We measured the body size of individuals of both species collected at the gradient's extremes. We found that the two Pardosa species occurred syntopically but had clearly differentiated spatial niches along the canopy openness gradient. Pardosa lugubris displayed a preference for closed canopies in dense forest habitats and its abundance gradually decreased as the canopy opened while the opposite was the case for P. alacris. The two species also differed in body size. Each species was larger at its preferred gradient extreme than was the other species. The coexistence of the two Pardosa species was mediated mainly by spatial niche partitioning. Body size differences may represent another axis for niche partitioning.

During collecting episodes in urban southern California, brown widow spiders, Latrodectus geometricus C. L. Koch, 1841, were observed to reside most often in specific locations such as acute angles within patio furniture or on the underside of railings. In this laboratory study, we tested several variables to determine which factors brown widow females may use for web site selection. All tests were conducted with corrugated cardboard refugia in enclosed dome-shaped insect cages. Brown widows were found to significantly prefer: 1) 30º angles compared to 60º or 90º angles, 2) cavities of 75 and 100 mm depth compared to 25 or 50 mm depth, 3) cavities lined with single-faced corrugated cardboard compared to smooth surfaces, and 4) refuges that had previously housed a brown widow compared to similar but previously unoccupied refugia. These data provide unusually detailed information about microhabitat selection by an urban pest, with possible implications for the pest control industry for eradication or for home owners to avoid envenomations.

Homalonychus selenopoides Marx, 1891 is endemic to the Sonoran Desert in Mexico and the southwestern United States. Despite its wide distribution in the desert, nothing is known about its phenology. For this study, we collected 464 immature and adult spiders and 67 egg sacs during late 2007 and throughout 2008. In the field, the life cycle is annual and phenology is markedly seasonal. Egg sacs and 2^nd instar spiderlings occur in the field only from April–July, juveniles throughout the year, penultimate spiders from September–April, and adults of both sexes from November–April. Temperature and juvenile frequency were positively correlated (r² = 0.9374; P < 0.0001), but temperature and adult frequency were negatively correlated (r² = −0.8904; P < 0.0001). These spiders are active in winter and this is when the adults mature and mate. The phenology model proposed fits the winter-mature pattern of Aitchison (1984). Reproductive diapause governs the seasonal development of this species, which is possibly semelparous and univoltine.

Three new species of the genus Chapulobunus Goodnight & Goodnight, 1946, are described: Chapulobunus asper sp. nov., Chapulobunus psilocybe sp. nov., and Chapulobunus regiomontano sp. nov. from the states of San Luís Potosí, Oaxaca, and Nuevo León, in Mexico, respectively. Additionally, an identification key to the five known species of the genus is provided.

Autotomy, the strategy of voluntarily releasing a leg during an encounter with a potential predator or in agonistic interactions between conspecifics, is common in animals. The potential costs of this behavior have been scarcely studied. In addition, locomotion and substrate-dependent performance might be affected by autotomy. We did a comparative and observational study to investigate whether losing legs affects the escape speed and trajectory of harvestmen in the genus Prionostemma Pocock, 1903 (Eupnoi: Sclerosomatidae) on different substrates: soil (the least roughened), smooth bark and mossy bark (the most roughened) in a tropical premontane forest in Costa Rica. We observed that 71% of the individuals found were missing at least one leg. Harvestmen, regardless of leg condition, walked faster and made fewer turns in their trajectory in the soil. While climbing, they were faster on smooth bark than in moss. On all substrates, autotomized individuals were slower and had a more erratic trajectory than intact ones. The type of missing legs (sensory or locomotor) had no influence on the speed or trajectory. We experimentally induced autotomy and found that walking speed on soil decreases if individuals lose a leg. Our findings confirm that losing legs affects locomotion, and we provide novel insights on how locomotion in these harvestmen depends on surface roughness. Our data suggest that moss could be a type of substrate that requires more elaborate skills in balance, orientation and texture recognition than smooth bark.

We report on the feeding by black bears on harvestmen (Opiliones). Two scats of black bears from Sonora, Mexico each had over 50 bodies of a species of Leiobunum C.L. Koch, 1839 collected in localities separated by 5 km. Microsatellite analysis indicated that the scats were from different individuals. That all harvestmen were found in only two of the 180 scats sampled suggested that the two bears fed on harvestmen while in aggregations. Because black bears are probably minimally affected by defensive compounds and would presumably not actively search for individual harvestmen, black bear predation on harvestmen, if frequent enough, would be a factor selecting against aggregative behavior in these arachnids in the study area. Further research is needed on the aggregation behavior and other natural enemies of harvestmen in northwestern Mexico.

Of all scorpion species described to date, only a small fraction are known to reproduce without fertilization by a male, instead producing offspring by parthenogenesis. Here we show that isolated females of the buthid Pseudolychas ochraceus (Hirst, 1911) are capable of parthenogenetic reproduction and we provide data on the postembryonic growth of this species.

We present a first analysis of the ecology and potential distribution of Euscorpius carpathicus (Linnaeus, 1767), a scorpion species endemic to southern Romania, and report on the overwintering habitat selection of this species. Using field data, literature review, species distribution modelling, and habitat selection models, we document the broad scale distribution and ecology of E. carpathicus, as well as habitat selection in the foothills of the Curvature Carpathians, including exclusive microhabitat selection of riverine clay banks. In contrast with other species of the genus that inhabit cracks in cliffs or walls, E. carpathicus has adapted to cracks in clay.

Most web spiders use chemical and vibratory cues for intersexual communication prior to mating. Little is known regarding the behavior of the web spider, Pholcus manueli Gertsch, 1937. In the laboratory, we examined the behavior of males in female webs. Some webs were washed and allowed to air dry. Both washed and unwashed webs were tested with and without females. Overall, male behaviors were similar to courtship reported for other pholcid species and their frequency was related to male size. Web washing delayed the initiation of activity, reduced abdomen flexes, and increased the likelihood of pedipalp expansion and aggression. The presence of females caused males to initiate movement sooner and to increase silk pulling behavior. These results suggest that courtship is multimodal and that the vibratory dialog between males and females works along with chemical communication in this species. Hopefully, these data will enhance future studies of sexual selection in pholcids.

Detailed descriptions of sperm induction are rare in the literature. Anelosimus vierae Agnarsson, 2012 (Theridiidae) is a Uruguayan subsocial spider that lives in communal nests. This paper describes the sperm induction of this species under laboratory conditions. We collected spiders in Montevideo, Uruguay, from different trees and placed them in thirty male and female pairs in Petri dishes to observe the occurrence of sperm induction. We witnessed twenty-two males performing sperm induction after copulation. Sperm web characteristics and description of the male's behavior during sperm induction are described.

Although sexual size dimorphism is a widely observed phenomenon in nature, the selective forces that led to it are still controversial. Here we study sexual dimorphism in the static allometry of the legs of a large ground spider, Grammostola rosea (Walckenaer, 1837). We found that this species has a moderate sexual size dimorphism and males have longer legs relative to body size than females, similar to other ground spiders. We propose that male mate searching behavior may be a relevant factor in the genesis of this phenomenon. The longer extremities in males with respect to mass than in females would lead to an optimization of the costs associated with locomotion, because males have smaller masses and longer legs than the females both in absolute terms and relative to body mass.