The Nearctic agelenid spider genus Agelenopsis Giebel 1896 is revised, with redescriptions of the 13 known species including: A. actuosa (Gertsch & Ivie 1936), A. aleenae Chamberlin & Ivie 1935, A. aperta (Gertsch 1934), A. emertoni Chamberlin & Ivie 1935, A. kastoni Chamberlin & Ivie 1941, A. longistyla (Banks 1901), A. naevia (Walckenaer 1841), A. oklahoma (Gertsch 1936), A. oregonensis Chamberlin & Ivie 1935, A. pennsylvanica (C.L. Koch 1843), A. potteri (Blackwall 1846), A. spatula Chamberlin & Ivie 1935, and A. utahana (Chamberlin & Ivie 1933). We also include an identification key to the species and a species distribution map. Our cladistic analysis of Agelenopsis is based upon 31 genitalic and somatic characters using Hololena hola (Chamberlin 1928) as the outgroup taxon and including three species of Barronopsis Chamberlin & Ivie 1941 in the analysis since Barronopsis has been considered a sister taxon to Agelenopsis in previous work. The cladistic analysis found 22 most parsimonious trees unambiguously supporting Agelenopsis monophyly. The majority rule consensus provides support for a clade including (((A. pennsylvanica A. potteri) A. actuosa) A. emertoni); another clade including ((((A. aleenae A. spatula) A. aperta) A. kastoni) A. naevia); and a third clade including ((A. oregonensis A. utahana) A. longystyla). Our analysis supports species groups proposed by researchers using molecular characters.

Plantation forests are being planted at an increasing rate and account for 7% of the global forested area. The majority of planted forests are composed of exotic tree species, and Eucalyptus trees have become the most widely planted hardwood species in the world. While Eucalyptus plantations have economic importance, their role in native biodiversity conservation, especially in areas without naturally occurring forests, is little explored. In the present study, we assessed the impact on biodiversity of replacing natural semi-deserts with Eucalyptus camaldulensis plantations. The impact was evaluated by comparing epigeal spider communities of seven plantations with previously sampled communities of seven natural habitats in the northwestern Negev, Israel. In contrast to our assumptions, spider species richness was higher in Eucalyptus plantations compared to natural semi-deserts. However, substantial differences in species composition between the two habitat types were observed. Few species found in natural semi-deserts were sampled in the plantations, suggesting that Eucalyptus plantations cannot substitute for natural semi-desert habitats.

Predators can affect prey indirectly by eliciting changes in behavior, morphology, and life history. These nonconsumptive effects are often mediated by predator cues used by prey to avoid capture. However, predator cues can cause stress responses in prey that negatively impact survival and reproduction. We explored responses of the wolf spider Pardosa milvina (Hentz 1844) to cues from the larger wolf spider Tigrosa helluo (Walckenaer 1837) and the ground beetle Scarites quadriceps Chaudoir 1843. We exposed Pardosa to cues from both predators and measured changes in body size, weight, consumption, and lifespan. We found significant effects of predator cues only on female longevity: females exposed to Tigrosa cues had shorter lifespans than those exposed to cues from Scarites. The lack of treatment effects on energy intake suggests that predator cues act through physiological pathways. Future experiments may uncover opposing hormonal mechanisms underlying the observed differences in lifespan.

Previous work has shown that jumping spiders are able to associate visual cues with shock. We tested the efficacy of vibration as an aversive stimulus. Phidippus audax (Hentz 1845) (Salticidae) were first allowed to choose between two video stimuli, a cricket and an oval. We then tethered spiders so they were oriented toward their preferred stimulus with their tarsi touching a platform, either vibrated by a motor (experimental group) or with the motor turned off (control group). Spiders were then given a second opportunity to choose between the stimuli. Experimental spiders were significantly less likely to choose the stimulus that they viewed during training compared to control spiders. Spiders stalked and ate prey soon after experiencing the training procedure, suggesting that vibration caused no lasting harm. In addition, freely moving spiders avoided a vibrating platform, supporting the assertion that the vibration itself is aversive.

Despite the importance of tarantulas in the areas of medicine and veterinary science, there is very little information on parasitoid-tarantula interactions. The present study describes the case of an endangered tarantula, Brachypelma vagans Ausserer 1875, infested by an endoparasitoid in the field. Using DNA barcoding, we identified the parasitoid as the phorid Megaselia scalaris. With more than 500 fly larvae inside the host, this particular infestation can be considered severe. The size range of the larvae indicates infestation by all three larval instars. We discuss the possible mechanism by which the parasitoid is attracted to the tarantula and make important recommendations regarding improvements in tarantula-rearing conditions. Finally, this case study exemplifies the efficiency of molecular technology for parasitoid identification.

Cryptachaea Archer 1946 currently contains 75 species. The genus is considered related to Achaearanea Strand 1929, Hentziectypus Archer 1946, and Parasteatoda Archer 1946 but differs from them in having a male palp with a short to medium embolus, which is not articulated and not supported on the back of the cymbium; the base is fused to the median apophysis, located in the hood of the cymbium. The Cryptachaea epigynum has uncoiled ducts leading to a pair of simple subcircular spermathecae. Twelve new species of Cryptachaea are here newly described from South America, seven from Brazil: Cryptachaea cidae new species from the state of Rio Grande do Sul; C. alleluia new species from Minas Gerais and Paraná; C. spectabilis new species from Paraná; C. divisor new species from the states of Amazonas, Acre, Rio de Janeiro, and Paraná; C. floresta new species from Amazonas; C. ericae new species and C. propinqua new species both from the state of Rio Grande do Sul. Cryptachaea catita new species occurs in Brazil and Argentina. Two new species are from Peru (C. tambopata new species and C. paquisha new species) and two are from Bolivia (C. benivia new species and C. lavia new species).

Two new species of the genus Conothele Thorell 1878 of the trapdoor spider family Ctenizidae are described from India: Conothele giganticus, sp. nov. is described from the Ngengpui Wildlife Sanctuary, Mizoram in northeast India and C. khunthokhanbi sp. nov. is described from Manipur in northeast India. Like other known Indian Conothele species, these spiders are also strictly ground burrowing. Additional information on habitat and natural history is provided for both species.

We estimated a multigenic molecular phylogeny and reconstructed biogeographic history for the European harvestman genus Ischyropsalis C.L. Koch 1839 (Dyspnoi). To reconstruct historical biogeographic patterns we conducted an algorithmic VIP analysis which revealed patterns consistent with a vicariance-dominated history. The existing morphology-based systematic framework for Ischyropsalis is mostly inconsistent with molecular phylogenetic results, and a new informal system is established that recognizes three main clades and several sub-clades. Species-level analyses revealed two non-monophyletic species (I. pyrenaea Simon 1872 and I. luteipes Simon 1872); subspecies of I. pyrenaea are distant relatives, and are formally elevated to species (I. pyrenaea pyrenaea to I. pyrenaea and I. pyrenaea alpinula to I. alpinula). A preference for cryophilic microhabitats has favored the diversification of high-altitude and cave-dwelling Ischyropsalis species; molecular phylogenetic data suggest that cave-dwelling species have evolved multiple times independently.

Many animals build homes to which they return after excursions. However, the sensory and motor mechanisms that animals use to home are poorly understood. Sand scorpions, including Paruroctonus utahensis (Williams 1968), make burrows from which they emerge to hunt at night. These scorpions spend most of their surface time within about a meter of their burrow. Our goal was to create a laboratory environment conducive to scorpion homing behavior. Specifically, our objectives were to verify in-lab burrow use similar to field observations and to characterize scorpion movements in these artificial environments. Tests occurred in circular, sand-filled arenas (65 cm diam); in the center of each was a shelter (a small jar lid with openings for the scorpions to enter). We used IR cameras to film all trials from above in a room with a 14:10 hour light-dark cycle. Animals were tested over a 7-day period for their tendency to establish and return to their shelters on a normal day/night cycle. Time-in-shelter percentages showed significant evidence of shelter use, consistent with their normal burrow use in the field. In the second experiment, we wrote a MATLAB program to automatically track several hours of videotaped scorpion nocturnal movements. Animals spent most of their time along the arena walls but made intermittent forays across the arena center. When they returned to their shelters, their movements appeared to be direct and deliberate. This behavioral set-up will be useful in future attempts to deduce the sensory information these animals use to return to their burrows.

Habitat and microhabitat selection by spiders are influenced by abiotic and biotic factors, including vegetation structure, natural enemies, and prey availability. Some species are highly dependent on particular conditions, such as the presence of substrates where they remain camouflaged, constantly humid sites or the occurrence of plants bearing glandular trichomes. Others are distributed in areas that include a wide range of physical conditions and interact with several types of prey, predators and competitors. In the present study, we evaluated spatial distribution and substrate selection of two sympatric congeneric species with distinct body shapes and colors, Eustala taquara (Keyserling 1892) and E. sagana (Keyserling 1893), in an area of Atlantic Forest in southeastern Brazil. We focused on the following factors regarding habitat selection: i) distance from the border (forest edge or interior); ii) altitudinal distribution, ranging from 740 to 1294 m; iii) web height above ground level; and iv) plant species used for web attachment. All individuals of both species were located at the forest edge, especially on dry branches. However, they occurred preferentially in different host plants and altitudes. Eustala taquara individuals were strongly associated with Conyza bonariensis, and E. sagana with Hyptis suaveolens and C. sumatrensis. Dry branch preferences might be important to reduce species conspicuousness to visually oriented predators, such as birds and wasps. Spatial segregation between closely related species possibly minimizes interference interactions, such as competition for particular sites or prey items.

I recorded diel and seasonal activity patterns and behavior of the brown recluse spider, Loxosceles reclusa Gertsch & Mulaik 1940 in a free-ranging synanthropic population in northwestern Illinois. Recluse spiders are sit-and-wait predators that spend 85–90% of their nocturnal activity sitting motionless on a small network of silk they use for prey detection. Time not spent waiting for prey is typically occupied maintaining the web by laying down new strands of silk. Feeding and sexual behavior constitute a minute, but critical, portion of daily activity. Recluses were more active at night, but some were active during the day, especially in darker areas of the garage. Activity was relatively constant during the nocturnal hours. Recluse spiders became active in early to mid-May and ceased in mid-October. Beyond this, there was no consistent pattern observed in activity through these months. Sexual encounters were typically brief and similar to behavior reported in prior lab studies. Agonism was rare, but intraspecific predation was the most significant contributor to observed mortality. The most commonly captured prey in this population were spiders (Araneae, 25%), beetles (Coleoptera, 21%) wood lice (Isopoda, 15%), and crickets (Orthoptera, 13%). Recluse spiders were never observed actively searching for prey, live or dead. More than 80% of dead prey that were offered experimentally were not scavenged. Brown recluse spiders are not active scavengers; they are sit-and-wait predators that will take advantage of dead prey they happen to encounter during other activities.

Postmating cannibalism where a female attacks, kills and consumes a male after a sexual encounter is frequently influenced by certain male morphological and behavioral characteristics. We conducted behavioral assays in the laboratory to test the predictions that male Alpaida veniliae (Keyserling 1865) with larger absolute and relative size in relation to their mate and those having longer courtship and copulation duration would have lower probability of being cannibalized by females after a sexual encounter. We performed a set of mating trials exposing males of different sizes to virgin females. We observed copulation in 88.8% of mating trails; its duration was very brief compared to courtship. Only a few attempts (16.7%) of recopulations with the same female were recorded, and in all these cases the first copulation was significantly shorter than the mean copulation duration of those who had only one copulation. The percentage of postcopulatory cannibalism was 47.6%. There was no correlation between the relative and absolute male size and duration of courtship and copulation. Postcopulatory cannibalism was independent of courtship and mating durations but was affected by absolute and relative male size. Smaller males were more frequently cannibalized than large ones. However, it remains unclear whether sexual cannibalism in A. veniliae may be explained by female mate choice or whether smaller males are less able to escape or defend themselves. More studies are needed to understand the underlying factors of postcopulatory cannibalism of A. veniliae, as well as to elucidate their possible ecological and evolutionary implications.

Parental care entails physiological costs to the mother. These costs, even if dramatic, are usually reversible and do not result in mortality of the mother. In the spider Stegodyphus lineatus Latreille 1817 (Eresidae), maternal care is extreme and irreversible: mothers regurgitate food for the young and then die when consumed by them (matriphagy). We examined whether the mother's midgut tissues undergo structural changes in preparation for regurgitation and matriphagy. Our histological data show that the midgut diverticula (MD) tissues start to degrade during the egg sac incubation period. When the young emerge from the egg sac, the midgut tissues are partly liquefied and are retained within the MD. The degradation process intensifies when the female feeds her young by regurgitation and liquid tissue is observed within and among the diverticula lobes. The presence of the lumen of a diverticulum during the regurgitation process suggests that degenerated tissues enter the lumen and form the regurgitated fluid. At matriphagy, the abdomen is filled with liquid containing nutritional vacuoles, which the young imbibe after piercing the female's abdomen. We conclude that the MD undergoes a gradual degradation process that maximizes the nutritional potential of the female's body and finally enables complete consumption of her soma. These changes are consistent with the extreme semelparous reproductive system of S. lineatus, where a female invests all of her resources into a single reproductive event. This is the first demonstration of the mechanism underlying suicidal maternal care in an arthropod.

The effects of elevated CO₂ concentration on spiders were studied using third-instar spiderlings of the wolf spider Pardosa astrigera L. Koch 1878 in CO₂ climate chambers with two different concentrations of CO₂ (low, 370 ppm and high, 750 ppm). The food intake and total developmental period of spiderlings reared at high CO₂ concentration increased significantly, and the body length and weight of adult spiders decreased compared to those in the low-CO₂ group. The oviposition rate of female P. astrigera and the hatching rate of eggs did not differ between the high- and low-CO₂ groups, but the number of egg sacs and the total number of eggs produced by females from the high-CO₂ group decreased. These results suggest that elevated CO₂ concentrations are harmful to the growth, development, and reproduction of P. astrigera.

Darwin's naturalization hypothesis (DNH) states that the successful establishment of alien species is favored when the phylogenetic relationship between the colonizer and the recipient community is distant. From a population perspective, the establishment involves both the progressive increase in size and spatial distribution of the invasive population. In this study, we focused our attention on the spatial component of establishment, assessing the role of phylogenetic relatedness as a determinant of its extension. Following DNH, it is expected that alien species closely related to the native spiders would show narrower distribution ranges than alien taxa less related to the native species. We found 18 alien spider species in Chile; all of these are synanthropic and most are of African origin. Our results indicate a difference in range size between related and unrelated species but it was not statistically significant. Consequently, the results do not support DNH as an explanation of the distributional component of establishment of alien spider species in Chile. We conclude that ecological constraints do not affect the process of invasion of spiders; therefore, it is only time that determines the spread of alien spiders in this country.

The size and shape of the glue droplets along the spiral threads of orb webs play an important role in web function. Despite this, methods for estimating droplet volume are not well defined, with contradicting formulas published. Here we address the discrepancies in the published formulas with a mathematical derivation that assumes that a glue droplet conforms to a parabola along one side of the axial line. We confirmed the validity of our derived formula by comparing it with the results of numerical integration. We also document that a droplet continues to conform to a parabola as its volume changes with environmental humidity. Our formula can be applied simply by collecting the spiral threads, examining the droplets under a light microscope and measuring their length and width, making it easy to compare the droplets of different species collected at different relative humidities.