The scorpion Diplocentrus zacatecanus Hoffmann (1931) was originally described as a subspecies of Diplocentrus keyserlingi Karsch 1880 on the basis of six syntypes and was later elevated to species level. We designate a male lectotype and redescribe the species, including illustrations of the hemispermatophore of a male collected near the type locality. In this genus, the hemispermatophore is poorly sclerotized and lacks elaborate capsular structures, which are taxonomically useful in other genera. We review the variability in the hemispermatophores of males from one population, including five comparisons of the right and left hemispermatophores of the same males. Our results showed asymmetry in the length of the right and left hemispermatophores of the same individual. We also observed the presence of “crenulations” or “spines” in two different hemispermatophores (not complementary ones). We conclude that caution should be used when describing the hemispermatophore of only one male and considering it as diagnostic for the species, because of the high levels of intraspecific variation.

Euophrys ambigua C.L. Koch 1846 is again transferred, becoming Freya ambigua, COMBINATION RESTORED. This jumping spider species, native to northern South America, has been found in North America in the southern parts of two of the states of the USA: Florida (Broward, Hillsborough, Manatee, Miami-Dade, and Pinellas counties) and Texas (Cameron and Hidalgo counties). Previously known from Colombia, Suriname, Trinidad and Tobago, and Venezuela, it is now also recorded from Brazil and French Guiana. Two other names are reported as NEW SYNONYMS: Menemerus fannae Peckham & Peckham 1896 and Freya perelegans Simon 1902. A lectotype is designated for Menemerus fannae. The female of F. ambigua is described for the first time.

The genus Bagheera Peckham & Peckham 1896 is revised. Joining B. kiplingi Peckham & Peckham 1896 and B. prosper (Peckham & Peckham 1901), two new species are described, B. motagua sp. nov. from Guatemala and B. laselva sp. nov. from Costa Rica. Both sexes of these new species are described and illustrated. Additional illustrations of male palps, epigynes, male chelicerae and habitus of B. kiplingi and B. prosper are included for comparison, and the females of these two species are formally described for the first time.

Behavioral isolation may play an important role in speciation. However, the roles of divergence time and ecological specialization on the evolution of intrinsic barriers to gene flow are poorly understood. On the Galápagos, ecotypic differentiation of Hogna Simon 1885 wolf spiders has led to the repeated evolution of morphologically distinct high-elevation and coastal species on Santa Cruz and San Cristóbal. This offers a unique opportunity to investigate the importance of ecological factors and evolutionary history on courtship behavior, but also to explore the opportunity for interspecific gene flow. On San Cristóbal, both high elevation and coastal Hogna species clearly showed distinct courtship behavior. This pattern corresponded primarily with variation in male genital organs rather than with ecotypic classification or phylogenetic relationship. Despite low acceptance rates, heterospecific mating was observed, suggesting that potential gene flow within as well as among islands should not be neglected when seeking to understand island radiations.

Trait-mediated effects of predators can impact prey population dynamics by affecting prey behavior. The mirid bug Stenotus rubrovittatus (Matsumura) (Hemiptera: Miridae), a major insect pest in Japanese rice production, usually remains in the upper layer of paddies to feed on rice ears. However, the mirids are frequently trapped by horizontal webs of Tetragnatha spp. spiders, which are highly abundant in organic rice paddies, and fall to the bottom layers of paddies where they are preyed upon by ground-dwelling predators. It is hypothesized that Tetragnatha spp. spiders facilitate bug predation by wolf spiders through trait-mediated effects, in which their horizontal webs force the bugs onto or near the ground and thereby into the hunting zones of wolf spiders. Molecular gut-content analysis of 619 wolf spiders coupled with field measurements revealed that the number of wolf spiders that tested positive for mirid bug predation increased significantly with the density of Tetragnatha spp. spiders in the paddies. We also observed a positive relationship between Tetragnatha spp. abundance and total cover by their webs in paddies. We identified the potential for an unexpected interaction between an herbivorous insect pest and ground-dwelling spiders that usually inhabit different microhabitats in paddy fields by focusing on trait-mediated effects of webs built by Tetragnatha spp. Because spider webs occupy a certain proportion of the available space in terrestrial ecosystems, consideration of trait-mediated effects on interactions between flying insects and other predators may lead to a better understanding of local food webs.

Although our understanding of arachnid olfactory physiology remains relatively limited, studies continue to reveal the importance of chemical cues for many spider behaviors. Olfactory cues for detecting prey, navigating to foraging sites, or finding mates might be especially beneficial to cursorial and ambush spiders living in structurally complex habitats. Previous field results suggested that volatile plant chemical cues were important in Misumenoides formosipes Walckenaer 1837 (Thomisidae) navigation and led us to design olfactometer bioassays to test this hypothesis in the laboratory. In our olfactometer trials, crab spider males were attracted specifically to the floral scent of Rudbeckia hirta (a species on which M. formosipes is commonly found in the field), but not to volatiles from foliage of the same plant species nor to volatiles from foliage of Morus rubra. Male spiders also failed to display any attraction to the floral scent of Daucus carota, even though they commonly reside on that plant in the field. Female M. formosipes did not move toward R. hirta inflorescences as a first choice over a control, although they did spend more time in the olfactometer arm with the R. hirta treatment. Males' use of olfactory cues to locate R. hirta inflorescences should increase encounters with potential mates, given that females in our population are found on that substrate more predictably than on any other.

In the lycosoid spiders, the secondary eyes possess a grate-shaped tapetum lucidum that reflects light, causing eyeshine when these spiders are viewed with approximately coaxial illumination. This guanine-based reflective surface is thought to increase visual capabilities in low light. We explored the eyeshine of the posterior medial eye in eight taxa of pisaurid and lycosid spiders. The taxa included four pisaurids: Dolomedes tenebrosus Hentz 1844, D. triton (Walckenaer 1837), D. scriptus Hentz 1845 and D. vittatus Walckenaer 1837; and four lycosids: Gladicosa pulchra (Keyserling 1877), Hogna sp. (cf. Lycosa lenta (Hentz 1844) sensu Wallace 1942), Rabidosa punctulata (Hentz 1844) and Varacosa avara (Keyserling 1877). We found that there were significant family- and species-level differences in both the reflected spectra and the intensity of reflection. Although the peaks of the reflected spectra were in the green range for all spiders, the mean peak was further toward the blue end of the spectrum for the lycosids than for the pisaurids. Variation among species (about 54% of the total variation) was dominated by G. pulchra (Lycosidae) and D. vittatus (Pisauridae), both of whose spectra peaked near yellow, vs. V. avara (Lycosidae), whose spectra peaked to the blue side of green. The lycosid spiders showed overall brighter eyeshine. However, when corrected for their larger eyes, the lycosid spiders' reflections were dimmer for their eye size than were those of the pisaurid spiders. These results demonstrate that the reflective qualities of the tapeta, and perhaps the absorptive qualities of other tissues and media that the light must traverse, vary widely among lycosoid spiders. This variation may signal both functional differences in visual capabilities and interesting developmental or selective histories within this clade.

The phenotype of animals is often determined by an interaction between genes and the environment. In spiders, recent work has shown that the nutritional composition of prey can have a large effect on the growth and reproduction of spiders. I tested whether the growth of juvenile spiderlings was affected by an interaction between the clutch and the diet on which they fed (i.e., high or low nutrient) in both a wandering (Tigrosa helluo (Walckenaer 1837)) and a web-building (Pholcus phalangioides Fuesslin 1775) spider. Diet was manipulated by feeding spiderlings similar quantities of food that varied in their nutritional composition. The results for both species followed the same pattern. Overall, spiderlings fed the high-nutrient prey were larger, both in terms of mass and body size. However, there was significant variation in effect size among clutches, with some clutches showing large effects of nutrients on growth and other clutches showing little or no effect of nutrients on growth. In both species, there were no differences among clutches in the final mass and size of individuals on the low nutrient treatment. The differences among clutches were due to differences in the mass and size of spiderlings on the high nutrient treatments. These results highlight the importance of incorporating a diverse range of clutches or genotypes in studies of spider nutrition to ensure that the results are generalizable and not biased by particular genotypes or clutches.

Morphological studies have documented the tendency for male genitalia to diverge rapidly compared to other body parts in many animal groups, including spiders. But documentation of how differences in genital structures of closely related species correlate with differences in the behavior of their genitalia during copulation is rare. This study describes how the genitalia of the spider Leucauge argyra (Walckenaer 1841), a species in which both male and female have unusual derived structures, are used during copulation and compares their sexual behavior with previous descriptions of genital behavior in the congener L. mariana (Taczanowski 1881) and the genital morphology of other Leucauge species. Males of L. argyra have two prominent derived genital structures, both of which interact directly with the female; one of them apparently locks against a modified female structure, while the other is inserted into the female atrium. On the other hand, the most prominent derived female structure does not lock against or receive any male structure and may serve to sense movements of the male palp, perhaps to trigger deposition of a strong copulatory plug by the female. The female atrium is unusual in that it receives insertions of both the male's conductor and his cymbial hook. Both derived male structures of L. argyra may have evolved to stabilize the male's genitalia during intromission, perhaps in response to violent and dangerous female resistance or to perforate the strong plug that is probably produced or at least moved into place by the female. The rotating and projecting movements executed by male genitalia in L. argyra, which as in other spiders are presumably produced by the hydraulic unfolding of complex membranes in the palp, are quite different from the movements of the male genitalia of L. mariana. We speculate that in spiders in general, changes in palpal sclerites are often accompanied by changes in the movements of the sclerites, and thus by changes in the unstudied internal membranes of the palp.

Direct behavioral observations, plus deductions made from studying the lines in recently built webs, showed that Linothele macrothelifera Strand 1908 lays swaths of lines in relatively stereotypic ways that differ during sheet web and tube construction. Sheet construction occurs in brief bursts interspersed with returns to the retreat. The legs are not used to manipulate lines; the spinnerets attach lines to the substrate and are probably used as sense organs. Asymmetrical use of the spinnerets during sheet construction results in an increase in the variety of orientations of lines in the sheet.

Several recent studies emphasize, correctly, that the biomass of prey captured by an orb web is likely more important than the number of prey in driving the evolution of web designs. Using equations that estimate prey mass from the lengths of captured prey, one study concluded that rare, long-bodied prey contribute the large majority of energy obtained by orb weavers in general, and thus that the designs of orb webs should generally reflect selection favoring the capture of larger insects, especially the ability to absorb high-energy impacts. I show here that the weights of long prey have sometimes been seriously overestimated by these equations. In addition, the longer prey captured by spiders probably represent highly biased samples, in terms of both low weight/body length and low momentum/body weight, of the longer prey available in the environment, leading to overestimates of the kinetic energy that the orb needed to absorb to stop them. Deductions concerning how selection acts on orb designs that have been based on the prey captured are also flawed, because additional data on prey availabilities and prey escapes are needed to evaluate the possible gains and losses from different orb designs. Still another complication is that data on prey abundances in natural rather than altered environments are needed to understand past selection pressures that produced present-day web forms. I conclude that a dominant importance for rare large prey in orb web evolution has not been conclusively demonstrated to be a general rule for orb weavers. A more inclusive approach regarding orb functions is prudent, especially because many traits that improve some functions have opposite effects on others.

Bridging and ballooning dispersal in spiders are preceded by “tiptoe” behavior, in which the spider stands on the tips of its eight tarsi, with the legs extended downward and the abdomen raised, and releases one or more silk lines. The occurrence of tiptoe behavior has been used in experiments to indicate a propensity to initiate dispersal. Juvenile social spiders Stegodyphus dumicola Pocock 1898 (Eresidae) exhibited tiptoe behavior while walking along the upper strands of the capture web at night. Simultaneously, they released long silk lines that streamed upward. These behaviors were not followed by dispersal. In wind-tunnel tests we found that tiptoe behavior increased with time during the evening activity period and occurred with higher frequency in small individuals. We suggest that tiptoe behavior in juveniles of S. dumicola is not associated with dispersal, but is more likely a component of web-building.

The wandering spiders Ctenus amphora Mello-Leitão 1930 and Ctenus crulsi Mello-Leitão 1930 are sympatric in central Amazonian rainforests; however, the former is more abundant in sandy soils and the latter in clay soils. In previous studies authors suggested that C. crulsi is competitively superior on clay soils and avoids sandy soils. Thus, we hypothesized that these species differ in their responses to the soil type. To test this, we placed 37 C. amphora and 30 C. crulsi in chambers providing two choices (sand or clay) and compared the proportion of observations in each to evaluate both species' preferences. Ctenus crulsi significantly preferred clay to sand (P < 0.01), while C. amphora showed no evidence of preference between two types of soil. We discuss the possible ecological consequences of this difference in behavior. This is the first study that experimentally shows a difference between the responses of spider species to soil type as an explanation of their coexistence.

Little is known about the climbing habits of scorpions on plants, despite the interest in this behavior for understanding the connection between above- and below-ground food webs in deserts and to uncover the importance of prey availability and predator avoidance on foraging and habitat selection. Here we report on the foraging of Buthus cf. occitanus (Amoreux 1789) on shrub branches in an arid area in southeastern Spain. Black-light censuses were carried out within six 50 m × 4 m areas in one full and two new moon nights during September and October 2011. Shrub availability was estimated by counting shrubs in 50 m × 1 m areas within each census area. Results showed that nearly 40% of the scorpions, mostly small, 10–20-mm-long individuals, were found foraging on both inner and outer shrub branches up to 80 cm in height. The probability of finding a scorpion on a shrub was inversely related to scorpion size. Selectivity analysis showed that scorpions selected four shrub species, a result that may be related to prey size and availability. Foraging of B. occitanus on shrubs may be favored if this behavior not only allows access to shrub-inhabiting prey, but also reduces predation risk.