Based on specimens from several museum collections and recently sampled spiders during a field excursion to Mexico in 2014, the 11 species of Tegenaria s. l. endemic to the United States of America and Mexico are revised. Morphological characters and mitochondrial DNA sequences (CO1, NADH1, 16S) serve as the basis for proposed new combinations and new species. Tegenaria chiricahuae Roth, 1968 remains the only endemic Tegenaria species in the Western Hemisphere. All other specific names (T. blanda Gertsch, 1971, T. caverna Gertsch, 1971, T. decora Gertsch, 1971, T. flexuosa F.O. Pickard-Cambridge, 1902, T. florea Brignoli, 1974, T. gertschi Roth, 1968, T. mexicana Roth, 1968, T. rothi Gertsch, 1971, T. selva Roth, 1968, and T. tlaxcala Roth, 1968) are transferred to the genus Eratigena Bolzern, Burckhardt & Hänggi, 2013. Six new species are described: E. edmundoi, E. fernandoi, E. guanato, E. queretaro, E. xilitla, and E. yarini. In addition, females of E. flexuosa, and E. gertschi, and the male of E. florea are described for the first time. A phylogeny based on maximum likelihood analysis of combined mtDNA sequences, an identification key and images of all diagnosed species are provided.

Loxosceles rufescens (Dufour, 1820), the Mediterranean recluse spider, is a cosmopolitan species with toxic venom which can occasionally cause dermatological injuries in humans. Here, we report the finding of L. rufescens through intensive survey and exploration of six natural limestone caves in the western region of Thailand. These data provide the first direct evidence of L. rufescens living in large numbers in a natural habitat outside of their native Mediterranean range. Although the currently known distribution of L. rufescens in Thailand is quite narrow (the spiders were only found in one of the six caves explored), data on their biology and local habitat preferences are provided to better understand the colonization requirements of this species in the target area.

Brazil possesses the richest fauna of Salticidae in the world, including 560 species; however, no representative of the Brazilian fauna has been cytogenetically analyzed up to now. It has been demonstrated that karyotype data are a useful source for discussions on the phylogeny and chromosome differentiation of some salticid lineages. In this work, the first chromosome study of salticid species from Brazil is presented, with the addition of five genera to the 38 previously investigated worldwide. The analysis of mitotic and/or meiotic cells revealed 2n♂ = 28, X₁X₂0 in Asaracus sp., Coryphasia sp., Chira sp., Frigga quintensis (Tullgren, 1905), and Lyssomanes pauper Mello-Leitão, 1945. This karyotype constitution is the most common for Salticidae, occurring in species of distinct clades. The diploid number 2n♀ = 28 observed in Hasarius adansoni (Audouin, 1826) is unexpected, differing in one autosomal pair from the karyotype previously registered for males of the same species. The cytogenetic information reported here reinforces the wide occurence of 2n♂ = 28, X₁X₂0 within Salticidae, including species belonging to different clades and biogeographical regions. This karyotype is a shared character of Salticidae Philodromidae, found exclusively in these families within Dionycha, suggesting its sister relationship already proposed in the literature.

The European garden spider, Araneus diadematus Clerck, 1757, is one of the most common spiders in central Europe. However, despite its abundance, comparatively little is known about its internal anatomy. We therefore conducted an examination of the hemolymph vascular system (HVS) of A. diadematus, as part of a comparative survey on the circulatory system in spiders. The HVS of A. diadematus was investigated using micro-computed-tomography and serial sectioning and visualized using 3D-reconstruction software. In order to examine the HVS for intraspecific variability, over 30 specimens were studied in detail. The HVS of A. diadematus consists of a tubular heart, which is situated along the dorsal midline of the opisthosoma. Anteriorly, the heart gives rise to the anterior aorta and posteriorly to the posterior aorta. Three pairs of cardiac arteries originate from the dorso-lateral section of the heart and the branching pattern of these arteries in A. diadematus is visualized and described here for the first time. The anterior aorta runs through the pedicel into the prosoma where it branches to supply the muscles and organs with hemolymph. The central nervous system in particular is supplied by a large number of arteries, which show some interesting branching patterns, e.g., a unilateral origin of the transganglionic arteries in the subesophageal ganglion, and the supply of the lower lip by the first of these transganglionic arteries. Furthermore, there are a number of arteries in the HVS with unilateral (asymmetrical) origins. Some cases of intraspecific variability are demonstrated, e.g., for the arteries of the upper and the lower lip. The data presented here are discussed in reference to information on the HVS in Araneae available in existing literature.

Limb loss presents an interesting paradox: although it may permit escape from a potentially lethal situation, it may result in subsequent fitness-lowering consequences. Some studies have found costs of limb loss; others have not. If costs are high, they may dictate against retaining the ability to drop an appendage. I use a large data set derived from a long-term study of the crab spider Misumena vatia (Clerck, 1757) to investigate the role of several size- and time-related factors in evaluating the cost of losing variable numbers of legs, as well as of growing replacements. Specifically, do limb loss and regeneration affect condition, and do the results differ with sex and age? I focused on adult males because of their high frequency of forelimb loss, including loss of multiple limbs. Numbers of missing adult male forelimbs were correlated with date captured and mass (corrected for number of missing forelimbs), suggesting that the spiders lost forelimbs continually over the summer and that they reached progressively poorer condition than intact individuals, judged by a disproportionate loss in body mass. The frequency of forelimb loss by penultimate males matched that of adult males, but females and juveniles lost less than 1/10^th as many forelimbs as males. Males possessed many fewer partially regenerated forelimbs than missing forelimbs, but these frequencies significantly exceeded those for females and younger juveniles. Some information suggested that additional costs arose from the regeneration of forelimbs.

In mating systems that include semelparous reproduction and/or scramble competition, synchronous maturation of the sexes is vital for success. However, food limitation may alter the onset of maturation or the overall quality of the mature individuals and affect reproductive success. We examined the role of feeding history (well-fed vs. long-term deprivation) on female reproductive timing and its correlation with temporal patterns of receptivity behavior in the wolf spider Schizocosa ocreata (Hentz, 1844). We found that feeding history influenced developmental time and delayed maturation in long-term food-limited females. There was no significant difference in relative condition between treatments, yet well-fed females showed higher rates of receptivity. Peak receptivity behavior was correlated with the estimated overall mass of female ovaries/eggs, with females that possess larger ovaries and eggs showing more receptive behavior. This supports the hypothesis that while a food-limited female may attain maturity, the limiting factor underlying reproductive success is gonad maturation.

Sexual signals play a critical role in mate attraction, but fitness benefits of signal production depend on a number of external and internal influences. Sexual signaling can be energetically expensive, and has potential to attract unwanted attention from predators. Male brushlegged wolf spiders, Schizocosa ocreata (Hentz, 1844) (Araneae: Lycosidae), actively signal to females in the leaf litter habitat during their spring breeding season, but face a tradeoff between current and future reproduction as the season progresses. The terminal investment hypothesis predicts that with fewer available females, increasing risk of predation, and stronger influence of senescence as the season progresses, males should take greater risks to secure mating. We explored this idea by exposing males of increasing ages to female cues alone or female cues combined with predator cues. We found little or no direct evidence to support the terminal investment hypothesis in this species, in that males across all ages essentially ceased active courtship in the presence of predator cues, that is, there was no age related increase in courtship investment in the presence of predator cues. However, we found distinct evidence of senescence in males based on age-related changes in behavior, which has not previously been directly explored in this species. While males maintained similar levels of active courtship across all age classes (in the absence of predator cues), older males increased their relative investment in maintenance behaviors (grooming) and decreased non-courtship display behaviors such as tapping and leg raises. These findings suggest that studies of male behavior in this species should be carefully designed to control for age-related variation in behavioral response.

Rubber plantations in Southeast Asia have expanded greatly in recent decades, thereby increasing the amount of edges bounding natural forests. In this study, we focused on the effects of rubber plantation-forest edges on species diversity and abundance of web-building spiders. We also aimed to reveal environmental determinants that influence such patterns. We visually searched and collected spiders within 85 quadrats from October to January (heavy rain period), and 160 quadrats from May to September (light rain period). The quadrats were placed in five sites representing rubber plantations, rubber plantation-forest edge, and forest interior up to 150 m from the edge. We examined understory characteristics, microclimate, and potential prey within each quadrat. Certain species were abundant in rubber plantations, others were abundant at the edge or within the forest, and others showed no pattern. Species richness was not related to the edge whereas species diversity and total abundance of the spiders was higher in the rubber plantation and decreased at the rubber plantation-forest edge and into the forest interior. Temperature range and average temperature appear to drive the distribution patterns of species diversity and total abundance. Characteristics of understory, namely dry twigs and seedlings also tended to affect such patterns. Temperature probably affected the spiders' ability to maintain favorable body temperatures whereas dry twigs and seedlings probably provide reliable web support and suitable refuges.

Americovibone remota sp. nov. is described as the first New Zealand representative of the Ballarrinae, a Gondwanan-distributed group of harvestmen (Arachnida: Opiliones: Palpatores), from a female collected at Dart Hut in Mount Aspiring National Park. Though closely allied by external and ovipositor morphology to Americovibone lanfrancoae Hunt & Cokendolpher, 1991 of southern South America, A. remota lacks the reflexed pedipalpal tibia previously regarded as characteristic of the Ballarrinae. The genus Americovibone is restricted to austral Nothofagus forests which have a similar trans-Pacific distribution.

The morphology of arthropod intromittent organs evolves rapidly and is often species specific, phenomena widely attributed to sexual selection. Similar patterns in biomechanical properties may also exist, but practical challenges in manipulating small structures and measuring minute forces has impeded experimental biomechanical analysis. Here we describe a device that displaces a small structure while measuring its resistance, and use it to examine the biomechanics of penile flexure in the eastern North American harvestman genus Leiobunum C.L. Koch, 1839. Several Leiobunum lineages have lost primitive penis-associated nuptial-gift sacs and have gained apparent female pregenital barriers, a co-evolutionary pattern consistent with shifts from precopulatory enticement to more-antagonistic strategies. We tested for an association between losses of nuptial-gift sacs and increases in penile flexural resistance using five sacculate and five non-sacculate species. We measured three mechanical variables—resistance force, elastic efficiency and viscoelastic relaxation time—under lateral, dorsal, and ventral flexion. Our functional assumptions about sacculate and non-sacculate penes anticipated two biomechanically-defined species clusters, but three were found: a diverse sacculate group, a monophyletic non-sacculate group and an unanticipated mixed group. This work demonstrates that experimental genital biomechanics in arthropods is possible, and we discuss the functional implications of our results.

In order to study how sexual selection takes place during mating, it is necessary to have a clear knowledge of the interactions that occur throughout mating and which morphological and behavioral traits are involved. Available information about harvestman reproductive biology is mainly restricted to anecdotal field observations, most of them lacking a detailed description and quantification of mating behavior. In this paper, we study the reproductive behavior of the gonyleptid Pachyloides thorellii Holmberg, 1878 (Pachylinae) and provide quantitative and descriptive information about its sexual behavior. We observed 15 matings, measured females and males, and analysed our behavioral data in the context of individuals' sizes. We observed conspicuous pre-copulatory, copulatory and post-copulatory courtship. We also found that females have several strategies to reject males' mating attempts. Like most gonyleptids, males and females of P. thorellii mate in face-to-face position; however, we observed that both male and female clasp their chelicerae mutually. This behavior has not previously been reported for the suborder Laniatores. The information obtained through this study establishes the basis for further studies on this species' reproductive biology and supports the suitability of this species as a model to explore the importance of male copulatory courtship for female choice and sperm use.

A new genus and species in the South American sun-spider family Mummuciidae, Vempironiella aguilari gen. nov., sp. nov., is herein described from a series of specimens from the coastal desert of Punta Hermosa, Peru. Vempironiella can be readily distinguished from all other known mummuciid genera, by the absence of the cheliceral movable finger MM tooth and the presence of a diastema between the RFA and RFP teeth on the fixed finger. With this description, the number of valid species of mummuciids is 19, three of which have been described from Peru. Males of V. aguilari measure 3.90–5.85 mm in total body length making it the smallest solifuge species known to date. The cheliceral morphology of V. aguilari is discussed and some hypotheses on the function of morphology are provided.

The first American species of the pseudoscorpion family Feaellidae is named from specimens collected in the Atlantic Rainforest biome of southern Brazil. The lack of specialized setae on the movable chelal finger suggests that it belongs to a new genus and new species, which we name Iporangella gen. nov. and Iporangella orchama sp. nov., respectively. The only known population of I. orchama is located near Iporanga, São Paulo, and juveniles of an unidentified species are recorded from Ilha da Queimada Grande.

Intra- and interspecific coexistence has been recorded in several species of scorpions, reflecting different levels of aggregation and sociability. Some species of scorpions avoid temporal or spatial overlap of their surface activities, which may differ depending on species, age group or gender, and thus reduce intra- and interspecific competition and predation. We examined the surface activity of males, females and juveniles (sex-age class) of the scorpion Brachistosternus ferrugineus (Thorell, 1876) in an area of Arid Chaco, and also its microhabitat preference and behavior by each sex-age class. The month-by-month activity of each sex-age class was different, but all the classes were observed each month. The most frequently used microhabitat was soil (64.8%), while leaf litter and vegetation were used in similar proportions. The behavior most frequently observed was ambush (68.3%), followed by walking and less frequently feeding, doorkeeping and courting. Each sex-age class performed one particular behavior with more frequency than the others. Analyzing combinations of microhabitat, behavior and sex-age class, we found the juveniles were associated with feeding on vegetation, males with walking on leaf litter, while females were related to ambush on soil. No marked temporal distribution between sex-age classes was observed. However, the spatial distribution and frequency of behaviors were highly dependent on developmental stage and sex. These differences may facilitate understanding of the coexistence of different age-sex classes of B. ferrugineus.

Leucism is a congenital disorder in which the individual is born with partial hypopigmentation. It is quite common in vertebrates, but rare in invertebrates, especially in arachnids like scorpions. This paper presents the first record of this congenital disorder to be observed in the order Scorpiones. During field studies in the Area de Conservação Aldeia-Beberibe, a set of Atlantic forest fragments of 31,634 hectares, we collected a pregnant leucistic female Tityus pusillus Pocock, 1893. In this female, the variegated pattern described for the species was a lighter color than normal. The animal produced 10 normal juveniles (not leucistics). In addition, we analyzed 1,164 specimens from 17 populations deposited in the CA-UFPE to verify the frequency of leucism; there were no scorpions with leucism within the analyzed populations. Thus, a break in variegated pattern, as with the leucism described in this study, may increase the mortality rate due to predation.

During recent decades, the wasp spider, Argiope bruennichi (Scopoli, 1772), has expanded relatively quickly towards north Europe. As a consequence of its spreading, it is newly exposed to various factors of selection. We studied the impact of egg sac parasitoids on the mortality of A. bruennichi in three regions differing in climate conditions and time of settling by this spider. Parasitism of wasp spider egg sacs was relatively low (0–3.9%) and no significant differences between studied regions were found. One primary parasitoid, Tromatobia ornata, was reared; in approximately 60% of these parasitized cocoons, the entire content of the egg sac was destroyed.

Endosymbiotic bacteria are commonly found in terrestrial arthropods and their effects have been studied extensively. Here we present the first recorded case of endosymbiotic bacteria found in the spider family Anyphaenidae. A fragment of the cytochrome oxidase c subunit I “barcoding” region belonging to unidentified Rickettsiales, presumably belonging to the genus Rickettsia, was sequenced from six individuals of Amaurobioides africana Hewitt, 1917.