Spiders were once thought to have limited color production palettes, and even to lack melanin – one of the most ubiquitous biological pigments. Recent discoveries upend that view and show that the color production mechanisms in spiders are as elaborate as some of the more classically colorful groups of animals, such as birds, butterflies, and beetles. Here we summarize how colors are produced by spiders, identify gaps in our knowledge, show how researchers investigating color in different groups of animals can learn from each other, and suggest future opportunities for spider color research. Our understanding of color production mechanisms in other colorful groups of animals can be used as guidelines for discovering existing mechanisms previously unknown in spiders and vice versa. For example, spider species with colors potentially produced by the same kind of photonic structures previously described in white beetles, and in the blue/green scales of fishes and lizards are suggested here. In addition, novel principles first found in spiders that modify the iridescence of structural colors via the interaction of structural features across different length scales (i.e., micro-nano) may also be found in other colorful groups in the future. This review summarizes the state-of-the-art understanding regarding the proximate color production mechanisms in spiders, suggests a few future research directions that are likely to be fruitful, and facilitates the advancements in related fields, including the ecology, evolution, and functions of spider coloration.

Surgical removal and larval transplantation experiments were carried out to evaluate behavioral manipulative effects caused by larvae of the polysphinctine ichneumonid, Reclinervellus nielseni (Roman, 1923), on its orb-weaving spider host, Cyclosa argenteoalba Bösenberg & Strand, 1906 (Araneidae). Residual behavioral effects on spiders from which parasitoid larvae had been removed were recognized and are described. Some transplanted parasitoid larvae also successfully consumed alternative spider hosts provided to them, and completed metamorphosis. The removal experiment supports previous hypotheses proposed by Eberhard, that larval effects involve chemicals, which are still unidentified and are dosage-dependent, because (1) spiders with parasitoid larvae removed continued to show manipulated behavior, and (2) the later in their development that the parasitoid larvae were removed, the more acute remaining effects were (e.g., production of V radii, new hub loops and silk decorations on webs). Further, the results support the idea that the spider's web-building behavior is composed of independent units (modules), because whether or not specific web features were produced depended on when the larva was removed. Transplantation experiments provide a new technique for rearing parasitoid larvae whose host spider dies: penultimate instar parasitoid larvae were successfully reared following their removal from their original host by providing them with another host spider held by a mesh. Transplantation of a small young larva by gluing it onto another host that was released after successful transplantation, caused the new host to produce a modified web identical to the “cocoon” webs typically produced by parasitized spiders. This shows that venom injected by the adult parasitoid prior to oviposition is not necessary to induce behavioral changes in the host, which can be caused entirely by wasp larval secretions.

High throughput sequencing (HTS) has emerged as a valuable tool for the rapid isolation of genetic markers for population genetics and pedigree analysis. HTS-based SNP (single nucleotide polymorphism) genotyping protocols like RAD (Restriction-site associated DNA) sequencing or hybrid capture allow for the isolation of thousands of markers from any non-model organism. However, these protocols are relatively laborious and expensive and the resulting high marker density is not always necessary. Since HTS technology has also greatly simplified the process of microsatellite marker isolation and genotyping, we develop microsatellite markers as a cost-efficient and simple alternative to SNP genotyping. We present low coverage genome sequencing data from seven distantly related spider species (Argiope bruennichi (Scopoli, 1772), Larinia jeskovi Marusik, 1987, Oedothorax retusus (Westring, 1851), Pisaura mirabilis (Clerck, 1757), Australomisidia ergandros (Evans, 1995), Cheiracanthium punctorium (Villers, 1789), Theridion grallator Simon,1900) and show the utility of HTS for microsatellite isolation. We also present a simple Illumina amplicon sequencing protocol to genotype microsatellites from multiplex PCR amplicons in the Hawaiian happy face spider T. grallator. We discuss advantages and drawbacks of the use of microsatellites for a range of research questions, and highlight an unexpectedly fast decay and gain of repeat loci for T. grallator.

Spiders employ a wide range of foraging strategies and some are known to use conditional foraging behavior, which is tailored to the type of prey attacked. Little is known about the prey capture behavior of cribellate titanoecid spiders. Here, we investigated the fundamental trophic niche and predatory behavior of a cribellate-web spider, Titanoeca quadriguttata (Hahn, 1833). Juvenile spiders were collected under stones in a quarry and used in the experiment. We offered each individual nine prey types (spider, springtail, termite, cricket, cockroach, beetle, fly, moth, and ant) and observed the frequencies of capture and consumption, and the foraging behavior. We found that T. quadriguttata accepted many prey types, and thus, that its fundamental trophic niche was wide. The hunting behavior differed among prey types, depending on the size and potential danger of the prey. Two capture behaviors were used to overcome prey on the web. For dangerous and some large prey, such as spiders and crickets, the spider bit its victim and immediately retreated, whereas for innocuous and small prey, such as springtails and flies, the spider bit its victim and held it in the chelicerae. Attacks were administered to different body parts of prey. For example, ants were always bitten on the head, and crickets were bitten on the legs. We conclude that T. quadriguttata is an euryphagous generalist predator which uses conditional prey capture behavior to catch a variety of prey types.

The mygalomorph spider Aphonopelma hentzi (Girard, 1852) (Texas brown tarantula) is a geographically widespread and accessible system for the study of comparative development in spiders. However, remarkably little information is available regarding the timing of egg sac deposition and duration of embryogenesis in this species, a gap that can directly affect the success of field collecting efforts. Here, we describe the habitat, egg sacs, and embryos of A. hentzi in the Comanche National Grasslands of Colorado. We compare the effectiveness of strategies for obtaining adult specimens vs. egg sacs of A. hentzi from burrows. Protocols for rearing, fixation, fluorescent immunohistochemistry, colorimetric in situ hybridization, and imaging of embryos are detailed. Together with forthcoming genomic resources, these data are anticipated to improve understanding of embryogenesis in Mygalomorphae and comparative development of chelicerates more generally.

A review of the pseudoscorpion fauna from the Limatambo and Yanaoca districts, Cusco department, Peru, is presented. The species Parachernes (Parachernes) peruanusBeier, 1955 and Stenolpiodes gracillimusBeier, 1959, are reported for the first time for the Cusco department and a new species of Neochelanops, N. unsaac, is described.

Based on the recently published total evidence phylogeny of the family Stygnopsidae, the genus ParamitracerasPickard-Cambridge, 1905 was recovered as polyphyletic. As part of the revision of this polyphyletic genus, the Neotropical genus PanzosusRoewer, 1949 stat. rev. is resurrected from its synonymy under Paramitraceras. Panzosus is rediagnosed, the type species Panzosus hispidulus (Pickard-Cambridge, 1905) comb. rest. and the species Panzosus femoralis (Goodnight & Goodnight, 1953) comb. nov. are redescribed. Also, the following new species are described: Panzosus comayagua sp. nov., Panzosus cusuco sp. nov., Panzosus giribeti sp. nov., Panzosus marginalis sp. nov. and Panzosus roeweri sp. nov. An identification key for the species of Panzosus is provided, and a discussion of new morphological characters used for the recognition of the related genera Paramitraceras, PhiloraGoodnight & Goodnight, 1954 and SbordoniaŠilhavý, 1977.

A new species of the pseudoscorpion genus SpelaeochernesMahnert, 2001, Spelaeochernes popeyesp. nov., is described from male, female and nymphal specimens collected in limestone caves of the Canudos supergroup in northeastern Brazil. It differs from the other Spelaeochernes species by the spermatheca morphology and the absence of eyespots. It exhibits marked sexual dimorphism, with an enlargement of the male pedipalp hand, which may suggest a close relationship with S. armatusMahnert, 2001 and S. dentatusMahnert, 2001. However, the spermathecal morphology suggests a relationship with S. bahiensisMahnert, 2001. Spelaeochernes popeye sp. nov. is a guanobite, and only occurs in or near frugivorous guano piles and it was only found in subterranean domain, being considered as a troglobite.

The speed, precision and impact of strikes often determines predatory success. Whip spiders (Arachnida: Amblypygi) are nocturnal ambushing predators that use massive raptorial pedipalps in rapid strikes. While prey capture behavior has been described for a number of amblypygids, the movements performed during the strike have never been resolved in detail, in spite of their strong relevance for the feeding ecology and evolutionary history of this group. Here we studied the attack behavior of Charon sp. on crickets and describe the kinematics of body and pedipalpal movements during the strike. We found that the total strike is performed within 30–180 milliseconds with the pedipalpal tip being accelerated up to 70 m/s² during closure. We found that Charon sp. is able to strike the prey at a lateral angle of up to 30°, which is achieved by non-parallel abduction of the laterigrade legs. These results contribute to our understanding of the evolution of high performance of predatory structures.

The hymenopteran genus Zatypota Förster, 1869 (Ichneumonidae: Pimplinae, Ephialtini) comprises highly specialized koinobiont ectoparasitoids of spiders and is the largest genus of the Polysphincta group of genera in the world, with more than 50 described species. The vast majority of species of Zatypota are parasitoids of the spider family Theridiidae. In this study, we present information about a new interaction between the parasitoid spider wasp Zatypota riverai Gauld, 1991 and the host spider Theridion sp. Walckenaer, 1805 (Theridiidae) with information about host weight selection. We collected 102 non-parasitized adult and subadult females of Theridion sp. and six spiders with larvae of Z. riverai attached to host's abdomen. The pupal development takes about 8–11 days, though the development time of the pupa varies with the sex of the wasp. All larvae collected in the field completed their life cycle on the host spiders, even though all of the hosts were small, indicating that the host biomass was sufficient for larval development and no larger-sized spiders are needed. Moreover, larger Theridion probably pose a greater risk because they are more likely to be successful at wasp predation, even if they offer a greater resource to the larva.

Silk decorations in webs of orb-weaving spiders are considered visual signals. However, high pattern variation reduces the plausibility of a single signal function, and accordingly, current literature often presents contradicting explanations. The controversial question is whether specific web decoration shapes also serve specific functions or whether various arrangements can serve a single function. I studied inherent characteristics of the variation of silk decoration shapes in Argiope bruennichi (Scopoli, 1772), in the field and under invariant laboratory conditions. The results show, that even within a few days and with a small repertoire of patterns, A. bruennichi frequently varies the decoration shape. Field and laboratory data both reveal that this variation follows a predictable pattern, significantly differing from random. Spiders show a preference for two-banded decorations, omitting decorating altogether rather than building one-banded decorations. Since the shape matters to the spiders, this supports the idea of a single signal function in spite of the presence of web decoration pattern variability.

Stable between-group variation in collective behavior has been observed in a variety of taxa. We examine here whether climate of origin (arid/wet), colony personality composition (shy/bold/mixed), and group size determine the repeatability of collective foraging behavior in Stegodyphus dumicola Pocock, 1898 (Eresidae). Experimental colonies were created with contrasting ratios of bold/shy group members and run through 20 simulated prey capture events in a greenhouse. We found that (i) larger colonies and colonies composed of bold spiders were more repeatable in how many attackers they deployed to prey stimuli, (ii) colonies composed of shy spiders were more repeatable in their latency of attack, and (iii) climate of origin had no effect on the repeatability of colony behavior. Colony bold/shy composition had no effect on within-group variation in foraging behavior. Thus, differences in repeatability were the result of increases in between-group differences in foraging behavior, and not shifts in the behavioral flexibility of individual colonies. These results indicate that changes to colony composition and group size can alter the extent to which colonies exhibit characteristic behavioral differences.

In the Colombian orb-web spider Leucauge mariana (Taczanowski, 1881) (Tetragnathidae), both sexes contribute to mating plug formation. Males of this species show a conductor hook that could be involved in providing stability to the mating pair and used for mating plug removal. The aim of the study was to assess the relationship between the shape of the conductor hook in L. mariana and mating duration, the amount of sperm stored, and the occurrence of sexual cannibalism. We used geometric morphometric tools for studying the conductor hook shape. The width of the base of the conductor hook was negatively correlated with the probability of sexual cannibalism by females (PC2 = 0.017), but we did not find a significant relation with mating duration and the amount of sperm transferred. Female choice on male hook shape, or on the stability provided by the hook during the mating position, could be occurring in this species.

The reproduction of the yellow scorpion Tityus serrulatus Lutz & Mello, 1922 (Scorpiones: Buthidae) mainly occurs by parthenogenesis, and sexual reproduction is known for only a few populations. Recently, bacteria of the genus Wolbachia, a group of intracellular symbionts known to induce asexual reproduction in many groups of arthropods, were reported in a population of T. serrulatus. This finding suggests that the parthenogenesis in this scorpion could be caused by these bacteria. We tested the correlation between Wolbachia presence and parthenogenesis in T. serrulatus through PCR amplification tests of three bacterial genes (WSP, ftsZ and 16S) in parthenogenetic and sexual individuals. The results for Wolbachia were negative both in individuals from a sexual population and parthenogenetic individuals. This suggests that the Wolbachia infection previously reported for this species would be restricted to just the single population analyzed, or that the results previously obtained could be related to sample contamination.

Whip spiders (Class Arachnida: Order Amblypygi) are hypothesized to use multimodal sensory inputs to navigate back to their diurnal shelter after a night of activity, and chemical cues are thought to be involved. In two experiments, we investigated whether self-deposited chemical cues on a substrate could be used for shelter recognition by Phrynus marginemaculatus C.L. Koch, 1840. When given a choice, individual P. marginemaculatus spent more time in a shelter that contained filter paper it had previously contacted compared to a shelter with filter paper never contacted. In the second experiment, subjects showed no significant preference for a shelter that contained filter paper they had contacted compared to a shelter with filter paper that had been contacted by a conspecific. The data support the hypothesis that during the last stage of nightly navigation to their refuge, detection of self-deposited chemical cues, likely mediated by contact chemoreceptors, may facilitate home refuge recognition by P. marginemaculatus.

Research progress on the order Solifugae, commonly known as camel spiders, has been hindered by challenges inherent in collecting these fast-moving, nocturnal predators. Recently, pitfall trapping combined with artificial light lures showed promise for improving capture rates, but the hypothesis that camel spiders are attracted to light traps (positive phototaxis) has never been tested. We constructed short pitfall trap arrays with and without lights across the Mojave Desert to test the light attraction hypothesis. Nearly all camel spiders we collected were found in traps with suspended lights, lending strong support for positive phototaxis. Distance from the lights within trap arrays does not appear to be correlated with the success of individual pitfall traps. Excitingly, our short pitfall light arrays, or Caterpillar light traps, were relatively easy to install and yielded an order of magnitude more camel spiders per effort hour than previously reported techniques.