The jumping spider Maevia inclemens (Walckenaer, 1837) is unusual because there are two male types, tufted (T) and gray (G). We investigated the risks of predation associated with the different courtship strategies by testing the response of the predatory jumping spider Phidippus audax (Hentz, 1845) to T and G courtship display, to ascertain if the two morphs were equally noticeable. We then tested the courting responses of T and G in the presence of a conspecific mate and a potential predator (P. audax). For the first experiment, we used computer-animation techniques to present two different views of courting males: face-on view as a female might see a courting male; and 45°-above view as may be seen from the perspective of a predator hunting in the vegetation. Visual orientation distance to the courting male images was used as an estimate of predation risk. Results demonstrated that risk of visual detection was not equal for the males; P. audax oriented to G at significantly greater distances than to T. From the 45°-above view, the apparent size of courting G males measured approximately three times greater than that of T males, suggesting that from this point of view, T may be less conspicuous to predators. In our second experiment, T and G responded differently when courting a conspecific female if a live predator had recently been or remained in view of the male. Fewer G males courted than T males and the courtship latency was significantly longer for G than for T. The visibility of T and G males to both females and potential predators may help to understand how these different, but equally successful, courtship strategies are maintained.

Aerial dispersal in spiders or ballooning is typically considered to occur during the day by juvenile instars or small-sized adults. Allocosa marindia Simó, Lise, Pompozzi & Laborda, 2017 and Allocosa senex (Mello-Leitão, 1945) are two nocturnal wolf spiders that inhabit coastal sandy beaches of South America. As mothers of both species emerge from the burrows during the night to disperse the spiderlings, we expected that aerial dispersal of spiderlings could occur during that period. Our aim was to test ballooning occurrence in both species during day and night under laboratory conditions, using as a positive control, the wolf spider Schizocosa malitiosa (Tullgren, 1905). We examined ballooning behavior of once-molted spiderlings of A. marindia, A. senex and S. malitiosa, under diurnal and nocturnal conditions, recording observations in a container with grasses and sand as substrate. We exposed the spiderlings to air flow and recorded occurrences of climbing the grass, dropping on dragline and tip-toeing (pre-ballooning behaviors). The three species performed pre-ballooning behaviors during the day but also in the night, and the occurrences of these behaviors varied both within and among species. More events of pre-ballooning behavior were observed during the day than during the night. However, we found differences in the number of events of tip-toeing and dropping on dragline according to the time of the day. We discuss the possibility that microhabitat conditions could affect ballooning propensity particularly in the three coastal wolf spiders.

We examined patterns of vertical distribution within an assemblage of seven species of large wandering spiders in a lowland rainforest on the Caribbean slope of Costa Rica. Over 16 months, 22 trees were surveyed regularly at night, up to a height of 43 m, using a rope climbing technique. Local climate and canopy microclimate exhibited only weak seasonal fluctuations. There was a distinct vertical segregation between ground-dwelling and arboreal species. The arboreal species used almost the entire available height range, whereby immature Cupiennius coccineus F.O.P.-Cambridge, 1901 occupied higher parts of the trees than adults. The two most abundant arboreal species differed also in their use of arboreal microhabitats: while Cu. coccineus occurred most frequently on trunk bark and on epiphyte leaves, the smaller Ctenus sp. 4 was more restricted to trunk bark. We detected effects of structural complexity of the host trees but no effects of canopy microclimate or of local climate on vertical distribution of Cu. coccineus, by far the most abundant arboreal species. The differences in vertical distribution both between age classes of Cu. coccineus, and between Cu. coccineus and the smaller Ctenus sp. 4 suggest size-dependent habitat segregation in arboreal species along the vertical axis, which might diminish cannibalism and/or intra-guild predation. Moreover, the wide range of vertical distribution of arboreal spiders suggests that they may connect the understory and canopy food webs.

The locomotor activity of the Chilean recluse spider Loxosceles laeta (Nicolet, 1849), and the spitting spider, Scytodes globula Nicolet, 1849, were studied in the laboratory under controlled conditions (LD 12:12). In Chile, these are two common synanthropic spiders which share a microhabitat and show extensive thermal niche overlap. Although no systematic studies have been performed, it has been reported that they have nocturnal habits. Here we confirmed strictly nocturnal activity for S. globula and mainly nocturnal but with some degree of diurnal activity for the Chilean recluse spider. Also, S. globula showed a bimodal pattern of activity while L. laeta had a unimodal one. The similarity of the use of space and time make the interaction of these spiders inside homes highly probable.

Internal clocks, or circadian rhythms, are nearly ubiquitous across taxa (e.g., animals, plants, fungi, and cyanobacteria), and it is widely believed that a biological clock benefits organisms by enabling them to schedule behavioral and physiological changes in anticipation of predictable changes in environmental conditions. Theory and evidence suggest it is important that the internal clock resonate closely with the 24-h daily cycle. Recently, however, Cyclosa turbinata (Walckenaer, 1841) (Araneidae) was revealed to have a circadian clock with a period of about 19 h, which was presumed to be anomalous. Here, we report on the behavioral rhythms of a nocturnal orbweaver, Metazygia wittfeldae (McCook, 1894), from the same family. Under laboratory conditions of a 12:12 h light:dark cycle, we found that locomotor activity initiates shortly after dark, reaching a peak early in the dark phase, continuing at a lower level throughout the remaining dark phase, and then diminishing shortly after lights-on. Locomotor activity continued to cycle under constant dark conditions with a mean free-running period of 22.7 h. We also found a second component in the free-running activity (mean 11.5 h) which correlated very tightly with the free-running period. Thus, M. wittfeldae has what can be considered a typical circadian clock resonating with the 24-h day. Notably, however, there were two outliers close to the 19-h period observed in C. turbinata, suggesting that there may be sufficient variation in clock period among araneid spiders upon which selection could act leading to the short-period clocks in C. turbinata.

The crab spider Misumena vatia (Clerck, 1757) (Thomisidae) is an important sit-and-wait predator at flowers visited by nectar or pollen-seeking insects. Typically, female M. vatia molt into their adult stage when many insect-attracting flowers come into bloom, and the spiders quickly gain weight leading up to oviposition. Between 1979 and 2010, the first spider ovipositions shifted one month earlier, from late July to late June, at my study site in coastal Maine, USA, in accordance with a concurrent temperature increase of ca. 0.44°C and a lengthening growing season. Flowering times of the spiders' most important hunting site, common milkweed Asclepias syriaca, as well as recruitment dates of their most important prey, bumblebees Bombus spp., to flowering milkweed, advanced as well. The shift in spider oviposition times increased the feasibility of second broods, though I found no successful second broods in the field, and the success of such broods would be problematic because of heavy overwintering losses. Differing rates of change of spider, milkweed and bumblebee activity indicated decreasing synchrony among these species; in particular, lessening future hunting opportunities for the spiders.

We describe the remarkable egg sac of Benoitia lepida (O.P.-Cambridge, 1876) (Agelenidae) from the Negev Desert, Israel. It consists of four layers: (from outside) a papery envelope, an outer loose silk layer, a “dirt layer”, and an inner flocculent silk layer surrounding the eggs. The dirt layer consists of loess soil, and may include stones, snail shells, or twigs from the surroundings. Some sacs hang from a silken string over the female's web sheet, attached to barrier threads or overhanging vegetation. In these “hanging sacs”, the outer papery wall is shiny white and covers the inner layers completely. Other sacs (“attached sacs”) are attached to a top branch of a shrub, away from the female's web. These sacs often have little or no outer papery envelope; the outer silk wrapping encloses the branch, and the sac may be dull brown in color. We studied the species at two sites; at one the hanging sac type predominated, while at the other the attached type was most common. A field experiment revealed that the dirt layer is effective in protecting the sacs against predation from ants but had no effect on spider predators of the egg sacs.

Chemically induced predator avoidance behaviors exist in many arthropods. In this paper, we examined the behavioral responses of the desert scorpion, Paruroctonus marksi (Haradon, 1984), to airborne chemical cues from a natural predator, the larger scorpion Hadrurus arizonensis (Ewing, 1928). We used a Y-shaped, dual-choice olfactometer to test for avoidance behavior in the presence of a known predator, H. arizonensis. Prior to this study there has been little research done on chemically induced predator avoidance behaviors in scorpions. The results of this study suggest that P. marksi is capable of detecting a predator's airborne cues, though the nature and identity of these cues remain unknown, and it appears that the constellation array of the fixed finger does function in detecting these cues. We also discuss the importance of adaptive predator avoidance behaviors.

Even though less than 2% of pholcid species have been karyotyped, previous studies documented a wide diversity of diploid numbers and sex chromosome systems. Here, we increase the number of native Brazilian cytogenetically investigated pholcid species from three to eight and discuss implications of chromosome evolution in this group. The species analyzed here share a X0/XX sex chromosome system and biarmed chromosomes, but vary in diploid numbers, i.e., 2n♂ = 17 in Mesabolivar spinulosus (Mello-Leitão, 1939) and Mesabolivar togatus (Keyserling, 1891), 2n♂ = 15 in Carapoia sp., and 2n♂ = 9 in Micropholcus piaui Huber, Carvalho & Benjamin, 2014 and Micropholcus ubajara Huber, Carvalho & Benjamin, 2014. Chromosomal data indicate that most Mesabolivar species share a 2n♂ = 17, X0, while Mesabolivar luteus shares with Carapoia sp. a 2n♂ = 15, X0. This lends further support to the idea that M. luteus is in fact misplaced and more closely related to Carapoia González-Sponga, 1998. The diploid number of the two Micropholcus species is the lowest reported so far for spiders with monocentric chromosomes. The 2n♂ = 9, differs strongly from the 2n♂ = 17 previously reported for Micropholcus fauroti (Simon, 1887). As the number of autosomes of M. piaui and M. ubajara is exactly half of that found in M. fauroti, we hypothesize that the reduction occurred by an “all or nothing” fusion event. The low diploid number observed in M. piaui and M. ubajara is the first morphological synapomorphy that would support the establishment of a new genus to allocate the New World Micropholcus species.

Morphological studies of harvestmen usually investigate the structures of adults, seldom including data regarding ontogenetic differences in the microanatomy of the appendages. In gonyleptoidean harvestmen, adults have clusters of pores on the distal-most tarsomeres of legs III and IV that are known as tarsal aggregate pores (TAPs). In gonyleptid harvestmen, these pores occur on the prolateral and retrolateral surfaces as groups adjacent to the tarsal claws. In this study, we used scanning electron microscopy (SEM) to compare the microanatomy of the TAPs occurring on leg IV of adults and antepenultimate nymphs for three common species of Neotropical cosmetid harvestmen, nymphs of an additional seven cosmetid morphospecies, and adults and antepenultimate nymphs of three species of gonyleptoidean harvestmen. The distal tarsomere of leg IV of adult cosmetid harvestmen features two pairs of aggregate pores including dorsal TAPs and ventrolateral vTAPs. The TAPs of cosmetid nymphs have denticulate borders and are not closely associated with trichomes. We observed interspecific variation among cosmetid harvestmen with respect to the number of pores composing the TAPs. The TAPs on the prolateral and retrolateral surfaces occur in similar positions and are generally symmetrical with respect to overall shape and the number of pores. The functional significance of the TAPs and vTAPs of cosmetid harvestmen will require additional empirical evaluation.

We provide a first scanning electron microscopy examination of the Paleotropical harvestman family Podoctidae (Opiliones: Laniatores), focusing on the distitarsus of the legs of Metibalonius sp. Distitarsi I and II are mostly equipped with olfactory sensilla chaetica with wall pores, while those of legs III and IV have gustatory sensilla chaetica with a tip pore, ventral trichomes with ovate tips (non-sensory) and a type of spatulate seta. Spatulate setae are present in adults of both sexes, with no apparent sexual dimorphism, but they are absent in the nymph. Seven of these setae are inserted on the frontal surface of the last tarsomere of legs III and IV, with the tips oriented ventrally. Each seta has an s-shaped socketed shaft, which terminates distally in a spatula-shaped structure. The distribution of spatulate setae, restricted to legs III and IV (walking legs), the position on the distitarsi, and the typical spatulate shape suggest an adhesive function for these structures. Morphology and position suggest that the socketed spatulate setae of Metibalonius sp. and the previously reported scopular spatulate setae of other harvestmen constitute two distinct types of adhesive structures, highlighting the diversity of adhesive structures in Laniatores. Future investigations about the natural history of this species and internal morphology of spatulate setae are necessary to test further functional hypotheses and to determine their behavioral role.

The 22 species of Opiliones recorded from Iran are known from four families: one species of Dicranolasmatidae, five species of Nemastomatidae, 15 species of Phalangiidae, and a single species of Sclerosomatidae. Five of these are recorded for the first time from the country: Dicranolasma ponticum Gruber, 1998, Opilio nabozhenkoi Snegovaya, 2010, Phalangium armatum Snegovaya, 2005, Phalangium kopetdaghensis Tchemeris & Snegovaya, 2010, and Graecophalangium karakalensis Tchemeris & Snegovaya, 2010. An additional unnamed Rilaena species is known from the literature, but not included in the total number of species from the country. One new genus and two new species are illustrated and described as new from Iran. The new species are Opilio kakunini and Rilaena kasatkini. Goasheer, a new genus, is described to hold the species “Homolophus” iranus Roewer, 1952.

Five new species of the recently created genus Occidenchthonius Zaragoza, 2017 are described from caves of Portugal: Occidenchthonius alandroalensis sp. nov., O. algharbicus sp. nov., O. duecensis sp. nov., O. goncalvesi sp. nov. and O. vachoni sp. nov. The species Occidenchthonius cardosoi (Zaragoza, 2012) and Chthonius ischnocheles (Hermann, 1804) are reported from new localities in different karst units of Portugal. New morphological characters are proposed for use in the Chthoniidae taxonomy. An updated key to the genus Occidenchthonius is given.

An organism's ability to respond to ecological changes at its currently inhabited location, and to colonize a new one, is particularly important for organisms inhabiting ephemeral habitats. Phoresy, which involves attaching of a non-vagile individual to a selected carrier of a different species, is used by a wide variety of taxa, but surprisingly little is known about the genetic structure of phoretic species. A better understanding of their genetic structure would help elucidate the efficacy of this manner of dispersal. In this study, we analyse the phylogeographic patterns of the pseudoscorpion Chernes hahnii (C.L. Koch, 1839) across a 1830 km range, encompassing most of the species' distribution range in Europe. The lack of geographic structure and low divergences within the two main clades suggest that C. hahnii disperses by phoresy. Individuals shared haplotypes at localities 350 km apart and very little divergence was detected between localities over 1450 km away from each other, indicating that phoresy is a very efficient manner of dispersal in this species. We also detected highly divergent populations within C. hahnii; however, more material and additional data would be necessary in order to evaluate the potential existence of cryptic diversity within this species.

Two new species of ricinuleids of the genus Pseudocellus Platnick, 1980 are described based on adult males and females from Mexico: Pseudocellus quetzalcoatl sp. nov. and Pseudocellus olmeca sp. nov. from the same type locality in the state of Veracruz. The two new species represent the first record of two sympatric epigean species of ricinuleids for North America. The total number of described species of Pseudocellus from Mexico increases to 18, holding first place in terms of number of known ricinuleid species worldwide. With the two new species described herein, Veracruz, with four species, is the second state of Mexico with higher diversity after Chiapas, which has five recorded species. We describe for the first time, for any ricinuleids, pores on the membrane below the spermathecae, revealed using a staining technique. The function of these pores is unknown, although it is possible that these could be secretion glands for some kind of substance during the reproductive process. A taxonomic key for identification of males of species from Mexico and the southern United States is provided.

The aganippine spiny trapdoor spiders of the genus Eucanippe Rix, Main, Raven & Harvey, 2017 are revised, and six new species from south-western Australia's biodiversity hotspot are described: E. absita sp. nov., E. agastachys sp. nov., E. eucla sp. nov., E. mallee sp. nov., E. mouldsi sp. nov., and E. nemestrina sp. nov. Species of Eucanippe are among the most enigmatic of Australia's Mygalomorphae, with most taxa known only from pitfall-trapped male specimens. Little is known of their biology, natural history or burrow morphology, and a female specimen was unknown prior to targeted field work in 2017. This revision documents the known diversity of Eucanippe in Australia, and reveals a fauna dominated by species with restricted and largely non-overlapping distributions in the heavily-cleared agricultural zone of Australia's south-west.

The natural history and biology of the recently erected family Viridasiidae is virtually unknown, although members of Viridasius Simon, 1889 are frequently used in cladistical or toxicological studies. Therefore, we report on laboratory observations made of the feeding and mating behavior and describe the egg-sac of a species tentatively assigned to Viridasius. The spiders were mostly nocturnal and built a large, silken retreat for molting. Females built pendulum-like egg sacs consisting of a silken, string-like stalk and an oval repository. The egg-sacs were covered actively with substrate by the female. Our observations corroborate the positioning of the Viridasiidae outside of the Ctenidae, because pendulous and camouflaged egg-sacs are not known from any ctenid species to date.

The silk glands of the Western black widow Latrodectus hesperus Chamberlin & Ivie, 1935 are morphologically and functionally distinct. Studies of spider silk glands often show only high magnification images of sections or drawings of glands, making differentiation of dissected glands difficult. We dissect all of the gland types from L. hesperus females and show their gross morphology with light microscopy. Our micrographs portray the distinct morphologies and relative sizes of each silk gland type, consistent with prior descriptions of the silk apparatus of Latrodectus spiders. Notably, we verify the presence of two differentiated pairs of aggregate silk glands and spigots, thus resolving a discrepancy in the literature.

Damage to genital structures during copulation has been reported in about twenty spider families, but never in Lycosidae. Aglaoctenus lagotis (Holmberg, 1876), a South American wolf spider, is one of the few that live their whole lives in funnel-webs. This work reports on the damage to pedipalpal bulbs observed in males of the “southern Uruguay” form of A. lagotis with multiple copulations. Observed damage consists of the irreversible expansion of the hematodocha and even its explosion. A high copulation cost resulting from multiple and long-lasting copulations could be causing this damage, affecting the mechanism of sperm transference in a definitive way. This is the first report of pedipalp damage in lycosids, and also the first report of damage involving the hematodocha in spiders.

Males of several harvestman species fight for the possession of oviposition sites. Usually, males use spines and elongated appendages as weapons in these fights. Although males of many cranaids have spines that could be used as weapons, there is no report of male-male fights in this family. Here we describe the first case of a male-male fight in cranaids. Males of Phareicranaus aff. spinulatus face each other, extend their second pair of legs laterally, and use them to hit the second legs of the opponent. Pedipalps are kept above the chelicerae and not used to strike the opponent. The fighting behavior is remarkably similar to that described for Goniosomatinae (Gonyleptidae). We interpret morphological and behavioral similarities between cranaids and goniosomatines as convergences. Moreover, we suggest that body/egg size and predation pressure may have influenced the evolution of parental care and resource defense polygyny in these two harvestman clades.