The classification of jumping spiders (Salticidae) is revised to bring it into accord with recent phylogenetic work. Of the 610 recognized extant and fossil genera, 588 are placed at least to subfamily, most to tribe, based on both molecular and morphological information. The new subfamilies Onomastinae, Asemoneinae, and Eupoinae, and the new tribes Lapsiini, Tisanibini, Neonini, Mopsini, and Nannenini, are described. A new unranked clade, the Simonida, is recognized. Most other family-group taxa formerly ranked as subfamilies are given new status as tribes or subtribes. The large long-recognized clade recently called the Salticoida is ranked as a subfamily, the Salticinae, with the name Salticoida reassigned to its major subgroup (the sister group to the Amycoida). Heliophaninae Petrunkevitch and Pelleninae Petrunkevitch are considered junior synonyms of Chrysillini Simon and Harmochirina Simon respectively. Spartaeinae Wanless and Euophryini Simon are preserved despite older synonyms. The genus Meata Żabka is synonymized with Gedea Simon, and Diagondas Simon with Carrhotus Thorell. The proposed relationships indicate that a strongly ant-like body has evolved at least 12 times in salticids, and a strongly beetle-like body at least 8 times. Photographs of living specimens of all 7 subfamilies, 30 tribes, and 13 subtribes are presented.

Bark spiders (genus Caerostris Thorell 1868) are important models in biomaterial research due to the remarkable biomechanical properties of the silk of C. darwini Kuntner & Agnarsson 2010 and its gigantic web. They also exhibit female gigantism and are promising candidates for coevolutionary research on sexual dimorphism. However, Caerostris spiders are taxonomically understudied and the lack of a phylogeny impedes evolutionary research. Using a combination of one mitochondrial and one nuclear marker, we provide the first species-level phylogeny of Caerostris including half of its species diversity but dense terminal sampling focusing on new lineages. Our phylogenetic and morphological results provide the evidence for six previously undescribed species: C. almae n. sp., C. bojani n. sp., C. pero n. sp. and C. wallacei n. sp., all from Madagascar, C. linnaeus n. sp. from Mozambique and C. tinamaze n. sp. from the Republic of South Africa.

Three unknown species of Euathlus Ausserer 1875 (Araneae: Theraphosidae) are recognized and formally described. Euathlus diamante Ferretti sp. nov., E. sagei Ferretti sp. nov., and E. tenebrarum Ferretti sp. nov. are described from the Mendoza and Neuquén provinces of western Argentina. The cladistic analysis showed Euathlus as monophyletic supported by the following synapomorphies: i) male tibial apophysis with fused branches bases; ii) presence of a ventral spine on retrolateral branch of male tibial apophysis; iii) sternum longer than wide. According to this cladistics analysis, a tree topology of (Homoeomma uruguayense (Mello-Leitão 1946) (Plesiopelma longisternale (Schiapelli & Gerschman 1942) (Grammostola anthracina (C.L. Koch 1842) (Phrixotrichus scrofa (Molina 1788) (E. tenebrarum sp. nov. (E. truculentus L. Koch 1875, E. sagei sp. nov. ((E. parvulus (Pocock 1903) (E. condorito Perafán & Pérez-Miles 2014, E. manicata (Simon 1892), E. atacama Perafán & Pérez-Miles 2014)) (E. antai Perafán & Pérez-Miles 2014, E. diamante sp. nov.)))))))) is reported.

A new species of Paratropididae is described, Paratropis elicioi n. sp., representing the first record of the family Paratropididae from Ecuador. A key to the genera of the subfamily Paratropidinae is provided.

Two new species of Tangaroa Lehtinen 1967 (Araneae: Uloboridae) from the Cook Islands are described here: Tangaroa vaka n. sp. from Rarotonga, and Tangaroa pukapukan n. sp. from Mitiaro, both based on male and female specimens.

The Nannowithius group of the pseudoscorpion family Withiidae is newly defined, consisting of Nannowithius Beier, 1932 from northern Africa and the Middle East, and Termitowithius Muchmore, 1990 from east Africa. The group is characterized by the lack of a tactile seta on the posterior tarsi, and they are the only withiids to possess this character state. Both genera are associated as inquilines with social insects, Nannowithius with ants and Termitowithius with termites. Withius caecus Beier, 1929 and Plesiowithius dekeyseri Vachon, 1954 are redescribed and transferred to the genus Nannowithius, forming the new combinations N. caecus (Beier) and N. dekeyseri (Vachon). Plesiowithius is treated as a new synonym of Nannowithius. A revised description and new illustrations of Termitowithius kistneri Muchmore, 1990 are presented.

Pseudoscorpions of the family Withiidae are distributed in most regions of the world, but are less common in the Australian region. Apart from the cosmopolitan genus Withius Kew, 1911, the fauna is dominated by the endemic genera Metawithius Chamberlin, 1931 and Hyperwithius Beier, 1951. A review of material of both genera reveals that Metawithius is a senior synonym of Hyperwithius, and is defined by the presence of a patch of rugose cuticle on the internal surface of the male maxilla. The genus contains the following taxa: M. murrayi (Pocock, 1900), M. philippinus Beier, 1937, M. spiniventer Redikorzev, 1938, M. spiniventer pauper Beier, 1953, three species newly transferred from Hyperwithius to Metawithius, M. annamensis (Redikorzev, 1938), comb. nov., M. tonkinensis (Beier, 1951), comb. nov. and M. dawydoffi (Beier, 1951), comb. nov., and M. nepalensis (Beier, 1974) which is newly transferred from Withius. The remaining species previously attributed to Metawithius are transferred to other genera, primarily because they lack the patch of rugose cuticle. The subgenus Metawithius (Microwithius) Redikorzev, 1938 is once again raised to generic level, and provisionally contains four species, M. yurii Redikorzev, 1938 from southeast Asia, and M. indicus (Murthy and Ananthakrishnan, 1977), comb. nov., M. chamundiensis (Sivaraman, 1980), comb. nov. and M. bulli (Sivaraman, 1980), comb. nov. from India. Metawithius (Microwithius) tweediei Beier, 1955 also lacks the rugose patch of cuticle and is provisionally transferred to Withius, forming the new combination W. tweediei (Beier, 1955). Two new species from northern Australian rainforests are found to be most similar to Metawithius but instead of an internal patch of rugose cuticle, they have an external patch. These new species, R. bulbosus sp. nov. (type species) and R. longissimus sp. nov., are placed in a new genus, Rugowithius. Afrowithius Chamberlin, 1931 is regarded as a new synonym of Withius, and the type species Chelifer paradoxus Ellingsen, 1912 from South Africa is treated as a senior synonym of Withius crassipes (Lawrence, 1937).

Behavior can provide useful traits for testing phylogenetic hypotheses, and some details of orb web construction behavior have been especially useful in characterizing higher-level groups in spiders. The cues used to guide construction behavior and behavioral responses to these cues hold similar promise, but have never been used in phylogenetic studies. Here we use several techniques to test the hypothesis that orb webs in the two major branches of orb-weaving araneomorph spiders (Araneoidea and Deinopoidea) are monophyletic, using both the cues that guide orb construction and the spiders’ responses to these cues. If orb webs evolved only once, the expectation is that these traits should be similar in members of both evolutionary lines. This prediction was supported: species in the two groups use several of the same cues, and respond to them in similar ways. These cues include two identical reference stimuli for positioning sticky spiral lines; supplies of silk available in their glands that affect the positioning of sticky spiral loops; and at least one stimulus related to the size of the available space for the orb, which is used to trigger similar modifications of seven independent orb design traits. Neither group used tension-related cues to guide sticky spiral placement. These comparisons reinforce previous conclusions supporting orb web monophyly that were derived from morphological, molecular, and behavioral traits.

Crab spiders in the subfamily Thomisinae rank among the most extreme animals in terms of sexual size dimorphism (SSD). Hypotheses regarding the apparent selection for dwarfing of males relative to females generally reference advantages of small male size for mobility. Specific proposals claim that selection should be strongest in species with limited male-male combat, which would otherwise favor larger males. We aimed to determine if the predicted traits of low densities, female biased sex ratios, more movement by males, and limited male-male conflict characterized a population of Misumenoides formosipes Walckenaer 1837. New and previous assessments of these characteristics in this extremely dimorphic spider revealed a mix of support and discordance with the predicted set of traits. Repeated plot censuses over 2 years, together with daily monitoring of females and collections of males, documented relatively low densities with males outnumbering females by as much as 2.37:1. The movements of marked males were measured upon rediscovery during daily searches using two methods: tracking individuals from their point of discovery and trials in which males were moved to predetermined positions relative to females. Female movements were measured by marking their hunting positions followed by daily searches of these locations. Female average tenure across their locations was twice that of males (5.05 versus 2.45 days) and the initial moves made by marked males in trials were six times further than initial moves by monitored females (1.76 versus 0.29 m). Male-male conflicts over positions near females are frequent and intense in M. formosipes. By contrast, male fights are rare in the female biased populations of Misumena vatia, a species with similarly extreme SSD. Thus, while extreme SSD may be associated with enhanced mobility of small males during searches for females, it is not precluded by extensive male agonistic encounters.

The accumulation of microbes in and around the large, perennial nests of social arthropods can increase the potential for interactions between individuals and harmful pathogens. Accordingly, many social insects utilize multiple organizational lines of individual and collective defenses against microbes. The interaction between microbes and social spiders, however, has been almost entirely unexplored. Here, we use the social spider Stegodyphus dumicola Pocock 1898 (Araneae: Eresidae) to (1) probe how innate immunity varies among individuals and (2) determine if two types of silk extracted from their colonies can inhibit the growth of the entomopathogenic bacteria Bacillus thuringiensis. Individual spiders’ innate immunity against lyophilized cells of Micrococcus luteus varied negatively with their boldness, a behavioral metric important for individual foraging and the organization of collective behaviors. Further, silk from both the capture webs and retreats of uncontaminated colonies inhibited the growth of B. thuringiensis to a small degree. Thus, web construction might represent a form of collective anti-microbial defense in these social spiders. This preliminary evidence suggests that social spider societies may exhibit antimicrobial defenses on multiple levels of organization, including both individual- and group-level defenses.

Spiders (Araneae) are dominant predators in agro-ecosystems. Terrestrial seminatural habitats, such as hedgerows and grassy field margins, can enhance the abundance and diversity of spiders in adjoining fields, whereas the potential of riparian margins has rarely been studied. We compared the effects of hedgerows and riparian margins on aerial web-building spiders in adjacent cereal fields. While species richness and overall abundance did not significantly respond to distance from or type of field margin, each of the four dominant species responded differently. The abundance of Tetragnatha cf. montana Simon 1874 increased towards both hedgerows and riparian margins. Tetragnatha extensa (Linnaeus 1758) differentiated between field margin types and abundances increased only towards riparian margins. By contrast, Phylloneta impressa (L. Koch 1881) abundances decreased from field centers towards the field margins irrespective of the type. Type of field margin and distance showed an interactive effect on Mangora acalypha (Walckenaer 1802) abundances, which decreased from field centers towards hedgerows but changed only little towards riparian margins. Increasing spider densities towards field margins can be explained by the preference of spiders for adjoining seminatural habitats (overwintering, food availability, microclimate, vegetation structure), whereas increases towards field centers might be caused by interspecific competition and enhanced predation pressure near seminatural habitats and high prey numbers in crop fields. Overall, our study demonstrates that aerial web-building spider species respond differently to hedgerows and riparian margins.

Bioindicators could act as early warning indicators of environmental changes, ecosystem stress or taxonomic diversity. Pseudoscorpions have rarely been used as bioindicators, due to lack of information about their ecology, habitat selection, niche preferences and requirements, especially in southern Nothofagus forests. We studied the distribution and abundance of a pseudoscorpion species, Neochelanops michaelseni (Simon 1902), in different vegetation types (Nothofagus antarctica and N. pumilio forests, grasslands and peatlands) and examined how this species responded to different forest uses (harvesting and silvopastoral management), to explore its utility as a bioindicator. The study was conducted on long-term plots located at two ranches in Tierra del Fuego, using pit-fall traps during one summer. Neochelanops michaelseni abundance was higher in Nothofagus forests than in open ecosystems, which could be attributed to their affinity for litter and coarse woody debris. In N. pumilio forests, the pseudoscorpions were sensitive to harvesting, with similar abundances in harvested forests (aggregated and dispersed retentions) and grasslands. In N. antarctica forests, differences were not detected among unmanaged and silvopastoral managed forests, probably due to higher understory plant growth, and lesser diminishing of litter and debris by thinning than by harvesting. We conclude that the pseudoscorpion, N. michaelseni, can be a good bioindicator for ecosystem conservation and for evaluating recovery rate in the ecological conditions of impacted Nothofagus forests, and that management practice intensities should be regulated to create more suitable habitats for pseudoscorpion diversity conservation.

To obtain a reliable description of spider communities, robust sampling protocols are crucial. However, it remains unclear if descriptions of spider communities in tropical habitats require both day and night sampling. Here we tested whether sampling both day and night in high and low vegetation strata would lead to better diversity estimates of spider communities than sampling at only one period of the day. We determined spider taxonomic diversity in a network of 12 plots in French Guiana along a vegetation gradient. We found high alpha diversity of spiders as expected for a tropical area at every site. We showed strong differences in spider alpha and beta diversity between high and low vegetation strata, while they were similar between day and night sampling. Our results suggest that collecting spiders at only one period is sufficient to describe the diversity of spider communities across land use types in the neotropics.

A female Micrathena duodecimspinosa (O. P. Cambridge, 1890) used the elasticity of her long dragline to repeatedly jerk her newly constructed egg sac up and down as she lowered it into the leaf litter below. Jerking may reduce the chances that the sac will be entangled in vegetation before it reaches the leaf litter or help insert it deeper into the litter, where it is visually camouflaged.

A neotropical spider in the genus Janula Strand 1932 is reported as an opportunistic raider in damaged carton nests of the arboreal termite Nasutitermes ephratae. These spiders were shown to be attracted to ruptured nests and galleries from which they gather soldier termite prey that they bundle into silk-wrapped balls before suspending them away from the nests. Three species of Forcipomyia and one species of Atrichopogon (Ceratopogonidae, biting midges), rare associates of spiders, are reported as kleptoparasites on the dangling and immobilized termites.

The ambient temperature of an environment has potential to influence many aspects of the behavior and physiology of small-bodied ectotherms, including brush-legged wolf spiders Schizocosa ocreata (Hentz, 1844) (Araneae: Lycosidae). Temperature varies significantly, and often unpredictably, in their habitat throughout the spring breeding season, and is known to influence male Schizocosa courtship behavior. Currently unknown is what effect fluctuations in ambient temperature alone might have on critical, non-behavioral sexual signals such as female silk and chemical cues. We collected cues from mature, virgin females and subjected each sample to one of three thermal treatments (40°C, 20°C, or -12°C), at constant humidity. We presented treated female cues to mature males and recorded male response across treatment types as a behavioral indicator of signal degradation. There were no significant differences across treatments in the frequency or duration of male behaviors, including critical courtship and exploratory behaviors. Our results suggest that thermally induced degradation of female sexual signals is negligible for this species and likely has little or no influence on male behavior.