Lycosa apothetica Wallace 1947 is redescribed as a member of the genus Varacosa Chamberlin & Ivie 1942 based on genitalic morphology. The species is freshly illustrated, and information is provided as to its distribution and interesting characteristics.

This paper provides the description of a new species in the genus Zabius Thorell (Scorpiones, Buthidae), Z. gaucho n. sp., from four localities in the State of Rio Grande do Sul, Brazil. It differs from Zabius fuscus (Thorell 1877) and Z. birabeni Mello-Leitão 1938 in details of the telson shape, the longitudinal carinae on mesosomal tergites II-VI, and the number of pectinal teeth. The genus was hitherto known only from Argentina, Z. fuscus being a frequent inhabitant of the central Sierras; Z. birabeni, in turn, is probably a rare and non-orophilous scorpion, collected in scattered localities on the monte/chaco ecotone and in northern Patagonia. The presence of a species of Zabius in southern Brazil lends additional support to the generalized distributional track known as “peripampasic track,” which zoogeographically links the central Sierras Pampeanas with ancient mountains in the southern province of Buenos Aires, southeastern Uruguay and southern Brazil.

The cribellate amaurobiid genus Taira, which is suggested to be most similar to the genus Amaurobius and some other related genera, is revised based on genital characters. Eight species, one from Japan and seven from China, are included. Five new species from China are described: T. cangshan, T. concava, T. latilabiata, T. obtusa, and T. sulciformis. Titanoeca decorata Yin & Bao 2001 is newly transferred to this genus and its male is described for the first time. Taira lunaris Wang & Ran 2004 is newly synonymized with T. liboensis Zhu, Chen & Zhang 2004.

Quantifying primary sex ratios is necessary for studies in a wide range of areas including adaptive sex ratio modification, population demography, and sex-biased developmental mortality. Adult and penultimate male spiders are easy to sex, due to the great thickening of the male pedipalps, which are used for delivering sperm to the female reproductive tract. However, in many spider species, males and females are apparently monomorphic at hatching, are difficult to rear, and cannibalize their siblings, making assessment of primary sex ratios problematic. One technique for sexing spiders is karyotyping, but this can be challenging and time-consuming, particularly for species with high fecundity, and often requires destructive sampling. Here we report that, although apparently monomorphic, early-instar juveniles of two species of black widow spiders (Latrodectus hasselti Thorell 1870 and Latrodectus hesperus Chamberlin & Ivie 1935) can be sexed reliably. Palp width measurements are significantly different for males and females at the 3rd instar, with the palpi of juvenile females thinner than those of males. Moreover, sex identification with 89–100% accuracy can be achieved by an experienced observer visually inspecting the palpi of 3rd instar spiderlings under a dissecting microscope. Our results suggest that minimal investment in a pilot study can yield an accurate method for sexing juvenile spiders in the laboratory or field. The suitability of this method should be examined in other species with apparently monomorphic spiderlings, particularly those in which adult males have significantly enlarged palpi.

We investigated the activity pattern of males and females of the neotropical harvestman Neosadocus maximus Giltay 1928 focusing on behavioral variations between day and night and also between summer and winter. Our study also proposes a new method for quantifying arthropod behavior in captivity based on totally random samplings, which minimizes problems of pseudoreplication, so common in studies of behavioral repertoires. Eighteen individuals (nine males and nine females) collected at the Parque Estadual Intervales, São Paulo state, Brazil, were maintained in the laboratory from June 2003 to February 2004 for qualitative and quantitative observations. Thirty-four behavioral acts grouped in five behavioral categories were recorded, with “resting” (53.1%) and “exploration” (30.8%) being the most frequent. The behavioral repertoire of males (32 acts) was more diversified than that of females (29 acts). Moreover, there was a significant effect of sex (male × female) on the frequency of the behavioral categories: females expended more time resting than did males, whereas males expended more time in exploration and grooming activities than did females. There was also a significant effect of time of day (day × night) and of season (winter × summer) on the frequency of the behavioral categories: individuals were most active at night and during summer. Finally, temperature, but not humidity, had a positive effect on the activity of the individuals. In conclusion, the activity of N. maximus has sexual, daily, and seasonal variations, which are both quantitative and qualitative.

Patterns of sperm usage in multiply-mated females have profound fitness consequences for males, and create strong selective pressure on male behavior. In the cooperative theridiid spider Anelosimus studiosus Hentz 1850 adult males are tolerated in females' webs, and females have been observed to mate multiply with different males. In this experiment, virgin females were mated with two different males on consecutive days under controlled conditions to determine paternity patterns and behavioral responses of males to non-virgin females. The paternity of broods was analyzed using randomly amplified polymorphic DNA (RAPDs). Fifteen broods were analyzed and complete first male sperm precedence was found. Mating behavior differed between first and second males with the first males attempting fewer intromissions, but having a longer total time of intromission. This suggests that the second males are either prevented from normal copulation, or are reacting to the different condition of the females. The sperm precedence pattern is discussed with respect to its ramifications for male behavior, juvenile inclusive fitness, and the evolution of cooperative behavior.

Copulatory organ breakage, in which a portion of the male's genitalia breaks off and remains in or attached to the female's genitalia may represent a male strategy of high investment in a single mating. Such a strategy is expected when mating opportunities for males are limited and competition for females is high. We studied costs and benefits for males as a consequence of male organ breakage in the white widow spider (Latrodectus pallidus O. Pickard-Cambridge 1872). In order to estimate the frequency and consequences of such damage we provided each male with four virgin females simultaneously in an outdoors enclosure. We recorded male mating success and loss of the tip of the embolus (the male intromittent organ) inside the female's genitalia for each male. In order to test the effect of the broken tip as a mating plug, we collected females from natural populations and observed the location of embolus tips inside their genitalia. We found that damage to the male organ was frequent but did not necessarily result in male sterility. From the field data, we found that the likelihood of a second embolus tip entering the spermatheca is significantly lower than that of the first tip, suggesting the possibility that the tip functions as a partial mating plug.

Various orb weaving spiders decorate their webs with extra silk structures. In the araneid genus Argiope, these web decorations consist of flimsy aciniform silk threads arranged in zig zag shaped bands. The adaptive value of these structures is still unclear and controversy over a suite of possible functional explanations persists: the high variation of web decoration adds further uncertainty. Web decorations can differ in shape, size, and frequency across species and even within species. Physiological processes may influence individual variation in web decorating behavior. Molting events are major physiological transitions combined with fundamental alterations of the metabolic state of the spiders. For gaining new insights into possible proximate mechanisms driving web decorating behavior, we observed subadult Argiope keyserlingi Karsch 1878 females in the laboratory and registered the individual variation of web decorations associated with the maturity molt under laboratory conditions.

We found substantial individual variation of web decorations of A. keyserlingi. The most striking result was that subadult spiders built dramatically oversized decorations prior to the last molt. Since aciniform silk is used for both constructing web decorations and immobilizing prey we suggest that these extensive decorations might provide a store for the swift replenishment of aciniform silk after the molt. High silk recycling rates make temporary outsourcing less costly and facilitate a rapid resumption of prey capture following lost foraging opportunities during the molting phase. Thus, we argue that the solution of the riddle of web decorations might reside in the physiology of molting spiders.

In some spiders features of the webs of early instars may represent features of the ancestor's web. Some second instar spiderlings (first instar outside of the egg sac) of Tengella radiata (Kulczynski 1909) construct a small sheet web without any type of retreat. In subsequent instars, spiderlings construct webs that consist of a sheet with a small retreat that opens near its center. Webs gradually change as spiderlings growth and webs of 7^th instar spiders are indistinguishable from those of adult females. Spiders only begin to include cribellate threads in their webs during the 7^th instar. The growth of T. radiata is slow during the first three instars, but spiders' sizes increase steadily in the subsequent stages. Legs I of adult males are longer than in females, indicating an allometric growth that occurred mainly during the last molt of males.

Spider species diversity has been associated with vegetation structure and stratification but there are few studies comparing the spider distribution in different shrubs and trees. In this study we analyzed the species distribution of the spider community of 11 shrub and tree species in two different study sites in a Mexican tropical dry forest. We present results from multivariate analyses that explain their distribution. A classification analysis based on spider abundances separated one shrub, Croton ciliatoglanduliferus, from the rest of the plant species. This was explained by the presence of large numbers of the oxyopid Peucetia viridans (Hentz 1832) on this plant. A second cluster segregated broad-leaved from small-leaved, bipinnate species. This was mainly due to higher spider abundances in the latter type of plants. Four vegetation variables were estimated and their influence on the species distribution was assessed by means of a principal components and regression analysis. With the exception of P. viridans, all spiders were positively associated with number of leaves and number of branchlets per 50 cm branch and negatively with foliage area.

Vegetation as a preferred microhabitat for scorpions has rarely been considered despite many Buthidae (the bark scorpions) being non-burrowing errant scorpions that are active on both the ground and vegetation. Microhabitats can serve multiple functions for Centruroides vittatus (Say 1821), but a particular microhabitat can be preferred for a certain function such as a refuge, foraging, or feeding.

Observations of microhabitat use by C. vittatus were performed in Laredo, Texas of the Tamaulipan Biotic Province. Comparisons of microhabitat use by C. vittatus at different temperatures or precipitation levels were performed. Foraging and feeding by C. vittatus among microhabitat classes were also compared. The observed use of vegetation by C. vittatus during different seasons was compared to the expected use based on relative abundance of vegetation in the habitat.

Air temperature, but not precipitation, had a significant effect on microhabitat use by C. vittatus. Microhabitat had a significant effect on foraging of C. vittatus with caterpillars comprising 34.6% of the prey items and half of the scorpions feeding on caterpillars were in blackbrush (Acacia rigidula). The lowest proportion of scorpions observed feeding was on the ground (3.8%) and the highest in blackbrush (40.4%). The frequency of C. vittatus among vegetation classes was significantly different compared to the relative abundance of plant species in the plot. Scorpions were observed on prickly pear cactus (Opuntia engelmannii) and strawberry cactus (Echinocereus enneacanthus) at a higher frequency than expected, and scorpions were observed on guajillo (Acacia berlandieri) and tasajillo (Opuntia leptocaulis) at a lower frequency than expected. The frequency of scorpions on blackbrush was higher than expected during the spring.

Vegetation is an important microhabitat for C. vittatus in south Texas. The results indicate the possibility that C. vittatus in south Texas used various plant species to carry prey captured on the ground into vegetation to feed, used blackbrush to forage for caterpillars, and used strawberry and prickly pear cacti as a possible refuge.

Beating tray and sweep net samples from apple and pear orchards in south-central Washington State were used to obtain information on life history and phenology of orchard-associated spiders. Cardboard shelters placed in the orchards in the fall and collected during the winter yielded information on spider overwintering. Data were obtained for 43 species in 28 genera and 12 families. The eight most abundant species were Pelegrina aeneola (Curtis 1892), Meioneta fillmorana (Chamberlin 1919), Oxyopes scalaris Hentz 1845, Theridion neomexicanum Banks 1901, Misumenops lepidus (Thorell 1877), Xysticus cunctator Thorell 1877, Philodromus cespitum (Walckenaer 1802), and Sassacus papenhoei Peckham & Peckham 1895. Each was represented by more than 690 specimens. Salticidae, Philodromidae, and Linyphiidae were represented by the largest number of species. Most species appear to have univoltine life cycles in the study area. Species matured at different times during the season between spring and fall. Twenty-seven species utilized cardboard shelters for overwintering, but some common spiders failed to do so and apparently use alternative locations. Some species overwintered in a broad range of developmental stages, whereas other species overwintered in only one or two instars.

The potential distribution of the harvestman Geraeocormobius sylvarum Holmberg 1887 (Opiliones, Gonyleptidae, Gonyleptinae) from Argentina, Brazil and Paraguay, is modeled using the presence-only, GIS-based method Bioclim. The model was run on 2.5 min resolution climate layers using 19 derived bioclimatic variables. The bioclimatic profile of the species is described, and presumable limiting factors in each part of the range are discussed. Modeled distribution of G. sylvarum shows a remarkable correspondence to the Alto Paraná Atlantic forest ecoregion, with a marginal presence around the Araucaria forests and in gallery/flood forests towards the Southwest. Results support the 650 km yungas-Mesopotamia disjunction, as previously proposed, and reveal that localities in northwestern Argentina have extreme values concerning seasonality parameters with remarkably decreased rainfall in winter. Evidence suggesting that the disjunct pattern may have been derived by antropic introduction is briefly discussed.

Analysis of ecological data of the arboricolous nephilid spider Clitaetra irenae Kuntner 2006, endemic to Maputaland forests, South Africa, indicates the species' dependence on this highly threatened habitat. We tested C. irenae habitat dependence via GIS analysis by plotting the known distribution against southern African ecoregions. In the southern part of its range, C. irenae inhabits almost exclusively one ecoregion, the Maputaland coastal plain forests; but further north, in tropical southern Africa, it continues inland into Malawi's woodlands. We test and refute the hypotheses that C. irenae inhabits exclusively mature trees, trees of a particular species, trees with a smooth bark, tree habitats at certain height above ground, and only closed canopy forest stands. The ecological niche of C. irenae is flexible as long as suitable trees under at least partially closed canopy are available. We quantify the C. irenae ontogenetic web changes from orb to ladder and the simultaneous hub displacement towards the top frame. Such web allometry allows the web to increase vertically but not horizontally, which enables the spider to remain on the same tree throughout its development and thus the ladder web architecture is an adaptation to an arboricolous life style. Adult hub displacement, common in spiders with vertical webs, is explained by gravity. Clitaetra irenae web orientation on trees correlates with forest closure, and might indicate the Maputaland forest quality. We argue for utilization of the ecology of arboricolous nephilid orb-weaving spiders (Clitaetra and Herennia) in systematic conservation assessments in the Old World tropics.

A replicated pre- and post-burn study of survival of small and large Geolycosa xera archboldi McCrone 1963 and G. hubbelli Wallace 1942 in Florida scrub was conducted. These two syntopic species were chosen because G. x. archboldi prefers large gaps of barren sand in the scrub matrix, sites with little fuel for fires, whereas G. hubbelli strongly favors small gaps having some leaf litter, sites with modest or high fuel-loads. On the basis of these species-specific differences in microsite characteristics, I hypothesized that G. x. archboldi would be very fire tolerant but that G. hubbelli would be fire intolerant. I established two size classes for the Geolycosa: small spiders had 3–5 mm diameter × 5–9 cm deep burrows; large spiders had > 6 mm diameter × 10–17 cm deep burrows. Burrows of 25 spiders in each species × size class were marked before a burn in seven burn units (= fire management areas) and survival or mortality of each occupant was ascertained over the course of 5 days post-burn. Thus, the experimental design was 2 species × 2 size classes × 7 burn units × 25 replicates/burn unit (n = 700 spiders total). Survivorship was very high in small and large G. x. archboldi and in large G. hubbelli (93–96%), but it was low in small G. hubbelli (35%). Temperature recordings suggest mortality in small G. hubbelli was caused by high temperatures at depths of 5–10 cm during intense, but brief burns that characterize fires in Florida scrub. In contrast, large G. hubbelli had burrows sufficiently deep so that most of them did not experience lethal temperatures during burns.

A new species of the crab-spider genus Xysticus (Thomisidae), X. albertensis, is described from northern Alberta, Canada. Specimens are compared with those of three species that closely resemble them and live in the same geographical region, namely, X. chippewa Gertsch 1953, X. canadensis Gertsch 1934, and X. britcheri Gertsch 1934.

This paper describes an easy, cheap, and safe method of capturing and handling the medically important spider Phoneutria for venom extraction. The method does not injure or kill the spider and allows the extraction of pure venom.

The first description of the courtship behavior and copulation is provided for Tengella radiata (Kulczynski 1909). The male courts the female by rocking his body and vibrating his abdomen. These behaviors seem to induce the female to move out from her retreat onto the sheet and incline her body to facilitate intromission. The female has an active role during the courtship: strumming the tunnel and sheet threads, apparently inducing the male to increase the frequency and intensity of his courtship. Palpal insertion is extremely short. The female terminates the copulation by lunging at the male.

Instances are documented of salticids robbing ants by adopting a specialized behavior pattern, “snatching.” The salticid positioned itself beside an ant column on the wall of a building, repeatedly fixating its gaze on different individual ants in the column and maintaining fixation on the ant by turning its body while the ant walked by. When close to an ant that was carrying prey, the salticid maneuvered about so that it was head on, grabbed hold of the prey using its chelicerae, and then rapidly pulled the prey out of the ant's mandibles. Having secured the prey, the salticid moved away from the ant column to feed. All observations were made at Mbita Point, by the shore of Lake Victoria in western Kenya. The salticids were three species of Menemerus (Simon 1868): M. bivittatus (Dufour 1831), M. congoensis Lessert 1927 and an undescribed species, Menemerus sp. n. The ant species were from the genera Crematogaster (Lund 1831) and Camponotus (Mayr 1861). In all instances, the salticid was 2–6 mm in body length (juveniles of all three Menemerus species and adults of Menemerus sp. n). Prey items taken from ants were, in most instances, “lake flies” (adults of Chaoboridae and Chironomidae).

Excreta potentially provide parasites or predators with information about the presence of hosts or prey; hence, vulnerable individuals experience strong selection to minimize danger from this source. Alternatively or additionally, excreta could alert potential prey to a spider's presence. Adult female crab spiders Misumena vatia (Clerck 1757) exhibited a strong reluctance to excrete when retained under tightly confined conditions. Only 5% of regularly fed individuals (1% of total observations) excreted over observation periods of as many as 50 days while confined in 7-dram vials (5 cm high, 3 cm diameter). Individuals retained large amounts of excreta during this time. However, when released upon vegetation over two-thirds of them excreted within 5 min, after moving to the distal end of a leaf or petal such that the excreta fell below them onto lower vegetation or the substrate. In the field they showed little tendency to excrete close to their hunting sites. The ability to retain excreta should serve this relatively sedentary species well in situations where it suffers high rates of attack or may reveal its presence to potential prey.