Most arachnids are central-place foragers that return to retreats or burrows after excursions to hunt. In general, arachnids are relatively large and accessible to behavioral and physiological investigations, and in several cases the animals have special sensory structures that facilitate homing. Here we review the mechanisms used by non-arachnid walking animals to return to specific sites and compare them to what is known for several groups of arachnids. Much of what we know about path integration, in which an animal estimates the angle and distance of a homeward vector using information gathered during an outbound journey, has been gleaned through systematic behavioral experiments on spiders. We focus on the most heavily studied spider models, highlighting the methodology used to deduce various aspects of the path integration machinery. We also highlight some work being done on longer range spider navigators, and emerging work with other arachnid groups. We provide additional thoughts concerning the evolution of homing systems and suggest promising leads for further investigation.

In this paper, 374 incidents of frog predation by spiders are reported based on a comprehensive global literature and social media survey. Frog-catching spiders have been documented from all continents except for Antarctica (>80% of the incidents occurring in the warmer areas between latitude 30° N and 30° S). Frog predation by spiders has been most frequently documented in the Neotropics, with particular concentration in the Central American and Amazon rain forests and the Brazilian Atlantic forest. The captured frogs are predominantly small-sized with an average body length of 2.76 ± 0.13 cm (usually ≈0.2–3.8 g body mass). All stages of the frogs' life cycle (eggs/embryos, hatchlings, tadpoles, emerging metamorphs, immature post-metamorphs, adults) are vulnerable to spider predation. The majority (85%) of the 374 reported incidents of frog predation were attributable to web-less hunting spiders (in particular from the superfamilies Ctenoidea and Lycosoidea) which kill frogs by injection of powerful neurotoxins. The frog-catching spiders are predominantly nocturnal with an average body length of 2.24 ± 0.12 cm (usually ≈0.1–2.7 g body mass). Altogether >200 frog species from 32 families (including several species of bitter tasting dart-poison frogs) have been documented to be hunted by >100 spider species from 22 families. Our finding that such a high diversity of spider taxa is utilizing such a high variety of frog taxa as prey is novel. The utilization of frogs as supplementary food increases the spiders' food supply (i.e., large diet breadth), and this is presumed to enhance their chance of survival. Studies from Australia and South America indicate that frogs might be a substantial component in the diet of some mygalomorph spiders (i.e., families Atracidae, Idiopidae, and Theraphosidae). Many more quantitative investigations on the natural diets of tropical spiders are needed before reliable conclusions on the importance of frogs as spider food can be drawn.

Phoneutria Perty, 1833 is considered one of the most toxic spider genera in the world; however, the natural history and biology of these spiders is still largely unexplored. The objective of this study was to determine the natural diet of the medically important species Phoneutria boliviensis (F.O.P.-Cambridge, 1897) based on prey records from Colombia, and supplemented by published records found in electronic databases as well as photographic records from the internet. We found that P. boliviensis is an euryphagous predator with a broad diet made up predominantly of arthropods (orders Araneae, Blattodea, Coleoptera, Hymenoptera, Lepidoptera, Mantodea, Orthoptera, and Phasmatodea) and to a lesser extent of small vertebrates (Gekkonidae, Hylidae, and Sphaerodactylidae). These results support previous evidence suggesting that P. boliviensis is a generalist predator that includes both invertebrates and small vertebrates in its diet.

Clubiona pacifica Banks, 1896 is a common secondary occupant of lepidopteran leafrolls on alders (Alnus spp.). We collected rolled alder leaves at riparian sites in Washington State to determine seasonal phenology of C. pacifica and to examine egg laying and predatory activity. All stages of the spider occurred in rolled leaves, and spiders were found in rolled leaves throughout the season. Rolled alder leaves were used by C. pacifica as protected sites in which to molt and spend inactive periods and possibly to seek prey. Field observations and greenhouse experiments indicated that C. pacifica is capable of preying upon leafroller larvae. Occasionally, lepidopteran leafrolls were used by C. pacifica as ready-made chambers in which to oviposit, but more commonly the female spider herself folded an alder leaf to form a protective retreat for oviposition. These egg sac retreats and the associated egg sac are described and illustrated. After eclosion C. pacifica passes through a prelarval stage, a larval stage, and six nymphal stages before reaching adulthood. The principal period of reproduction and egg deposition is June and July, and most post-larval stages of C. pacifica appear to overwinter. We postulate that some individuals require two years to complete their life cycle although others may do so in a shorter time. Three ichneumonid wasps parasitized C. pacifica: Gelis sp. attacked the eggs; Schizopyga frigida and Zaglyptus varipes parasitized immature and adult spiders.

Diet composition of spiders may depend on several factors, such as the relative abundance of potential prey, microhabitat selection, structure and physical properties of webs, adaptations to attract specific prey, among others. Variation in diet composition is probably highly influenced by individual's spatial distribution and web design. In this study, we evaluated the population trophic niche breadths of two sympatric cobweb spiders, Nihonhimea tesselata (Keyserling, 1884) and Tidarren haemorrhoidale (Bertkau, 1880) (Theridiidae). These species build distinct webs in an area of Eucalyptus monoculture in southeastern Brazil. We collected their prey and also recorded parameters of webs like a height from the ground, distance from tree trunks, and distribution across the Eucalyptus stand. The diet of the two species was highly distinct. However, diet similarity was not correlated with the distance between webs. There was also no spatial segregation between species within the forest stand. However, N. tesselata used more distal portion of Eucalyptus branches than T. haemorrhoidale, which usually attached several threads to the tree trunk. In addition, diet restriction of T. haemorrhoidale may also be determined by the use of gumfooted threads attached to tree trunks (predominantly capturing ants), while aerial webs constructed by N. tesselata are more efficient at intercepting several groups of flying insects. Together, these differences in microhabitat and web design allowed effective resource partitioning among these two dominant predators in the studied plantation forest.

The harvestman genus VimaHirst, 1912 is revised and newly diagnosed. A new species from Caquetá (Colombia), Vima panita sp. nov., is described and illustrated. This is the second species of Vima, and it represents the first record of the genus from Colombia expanding its range by 1,500 km to the southwest. Scanning electron micrograph images of the body and photographs of the holotype of Vima insignisHirst, 1912 from Guyana, together with a map showing the distribution of the genus in South America, are provided.

The scorpion Tityus serrulatus Lutz & Mello, 1922 (Buthidae) is endemic to Brazil and is considered the most toxic South American scorpion species. The ample distribution of this species and its occurrence in urban areas has been attributed primarily to the parthenogenetic mode of reproduction. For a long time, only all-female T. serrulatus populations were known. Male specimens are very rare and have been recently discovered in natural environments within the Brazilian semi-arid zone. In the present study, we investigated cytogenetically bisexual populations of T. serrulatus, and compared the data with those available for parthenogenetic specimens. The diploid number (2n=12) and the general configuration of the chromosomes in male and female specimens were similar to those recorded for parthenogenetic populations. Male postpachytene cells contained chromosomes in a parallel arrangement with no differentiation of the bivalents, indicating the absence of heteromorphic sex chromosomes. However, the number of 28S rDNA sites varied between male and female specimens. Females invariably presented only one rDNA cistron, while all the males had two. This finding seems to indicate the existence of a sex-specific heteromorphism in T. serrulatus, in which the females are heterogametic and the males are the homogametic sex.

Spider silks are thought to have antimicrobial properties that prevent rapid degradation. Despite its biomedical potential, little research has focused on antimicrobial properties of spider silks. We tested the antimicrobial properties of gluey gumfoot capture threads of the western black widow spider, Latrodectus hesperus Chamberlin & Ivie, 1935, both for whole threads and after separating viscid silk from water soluble glue components using a water wash. Capture threads, unlike dry dragline silk, have a glue coating that may promote different interactions of bacteria with the material. Antimicrobial activity was assessed in an aqueous Escherichia coli cell culture and growth of colonies was counted over 24 hours. In contrast with previous research, mostly on dry dragline silk, we found an increase in bacterial growth for whole gumfoot thread treatment, but no effect of the solid and water-soluble components individually. These results suggest that better and proper procedures are needed for testing antimicrobials in silks, with controlled experiments using just one type of silk.

This is the first report on the parasitoids of egg sacs of Theridiosoma gemmosum (L. Koch, 1877) (Theridiosomatidae). The parasitic wasps Gelis melanocephalus (Schrank, 1781), Gelis mangeri (Gravenhorst, 1815) (Ichneumonidae) and Pachyneuron solitarium (Hartig, 1838) (Pteromalidae) were recorded as solitary parasitoids of egg sacs of T. gemmosum in Poland. The degree of parasitism of T. gemmosum egg sacs in three different years was 21.4–42.9%, and the reproductive fitness of female spiders in all cases of parasitized cocoons was zero. It seems that the suspension system of the egg sacs of ray spiders is not a barrier against egg sac parasitoids, including apterous species. We hypothesize that, at least in the case of G. melanocephalus, the size of the spider's egg sac is implicated in the ovipositional decision of the female parasitoid.

Chemoreception is a main sensory modality in harvestmen but there has been no experimental evidence of attraction to conspecifics by olfaction excluding contact chemoreception as an alternative explanation. Here, using a Y-maze olfactometer we tested whether the harvestman Mischonyx cuspidatus (Roewer, 1913) is attracted to volatiles of conspecifics. We found that males were attracted to volatiles of other males, but not females. Females were not attracted to female's volatiles, but were marginally more often attracted to volatiles of males. Our results help understanding mechanisms in mating and social behavior in the order Opiliones.

Behavioral studies of scorpions mainly focus on hunting and courtship activity. Few studies have focused on the cleaning processes that these arachnids invest in. This work aims to describe the first report of excreta grooming behavior for Brazilian scorpions. Excreta cleaning behavior was recorded in 37 specimens of Tityus pusillus Pocock, 1893 with the behavior lasting around 80 sec. The paste-like nature of the scorpion excreta suggests that it could easily obstruct their anus when dry, so the excreta cleaning behavior may mitigate this probability and further contact with the nitrogenous compounds.