There is controversy about the function of silk stabilimenta, also called silk decorations, on spiders' webs. Most of the proposed hypotheses have been tested using indirect methods. Protection against predators, advertisement for vertebrates to avoid web damage, and increasing prey attraction are the most popular hypotheses. In this study, I tested the prey attraction hypothesis on the silk decorations of the araneid Argiope savignyi using a trial tunnel built in the field, in which I exposed stingless bees Tetragonisca angustula to decorated and undecorated webs placed on wooden frames. I carried out two experiments: 1) a three-frame choice, consisting of a frame bearing a decorated web, one bearing an undecorated web and a control frame without web and spider; 2) a two-frame choice, in which the bees were exposed to only two frames consisting of “decorated web vs. control,” “decorated web vs. undecorated web,” and “undecorated web vs. control”. In favor of the prey attraction function, I found that decorated webs intercepted more bees than webs deprived of the decoration or controls with no webs. Argiope savignyi's decorations might lure prey to the web by UV-reflectance as it has been suggested for other Argiope species.

We used experimental manipulations to test adaptive explanations for the courtship display of the male widow spider, Latrodectus pallidus O. Pickard-Cambridge 1872. Two hypotheses have been suggested to explain a long and complex male display: a) Cooperation of males and females in the effort to physically stimulate the female. As the time of male arrival is not predictable, females may delay sexual readiness until the appearance of a courting male. b) Conflict between males and females regarding the display cost. Females impose on the males an energetically costly display that may last several hours as a test of their quality. To test both hypotheses, we manipulated the previous experience of either the male or the female. We presented naive or experienced males (males that had courted and were accepted by females but were prevented from copulating) to females that were either naive or experienced (had been courted by a male but prevented from copulating). We also presented naive males to mated females. Following the stimulation hypothesis, courted females were presumed to have been stimulated to mate and thus were expected to accept non-courting males as mates. Both naive and mated females, however, were expected to await male stimulation before allowing copulation. In contrast, the conflict of interest hypothesis predicts that the female tests each male for quality indicators and therefore a non-courting male should not be accepted as a mate. Mated females, however, should apply a less stringent test to courting males. Our results show that 1) naive females prevented males that did not perform a full courtship display from entering the nest and mounting; 2) naive males courted virgin females with the full display, independent of the female previous courting history; and 3) naive males shortened their courtship when presented with mated females. The results are consistent with the conflict of interest hypothesis.

Geolycosa grandis (Banks 1894) (Araneae, Lycosidae) is redescribed, and illustrations are provided for the first time. We propose that Geolycosa grandis be transferred to the genus Hogna Simon 1885. Hogna permunda (Chamberlin 1904) is synonymized with H. grandis. Notes are given on distinguishing H. grandis from similar species including H. helluo (Walckenaer 1837), Allocosa georgicola (Walckenaer 1837), and H. aspersa (Hentz 1844). Information on Lycosa permiana Scheffer 1904 is examined and the species is declared nomen dubium.

Plugging of female genitals via male sexual mutilation is a common sexual repertoire in some nephilid spiders (Herennia, Nephila, Nephilengys), but the behavioral pathways leading to emasculation are poorly understood. Recent work suggests that copulating Herennia males damage their reproductive organs during copulation and then voluntarily, and stereotypically, remove their pedipalps to become eunuchs. Presumably, such emasculation increases agility allowing the male to better fend off rival males. However, through our observation of male antagonism in Nephilengys borbonica (Vinson 1863) in La Reunion (Indian Ocean), we discovered that genital severance involving the entire male palp is induced by a rival eunuch. Additionally, laboratory matings of the same species from Mayotte provide the first observations of female sexual cannibalism in this species, one such forceful copulation termination leading to emasculation of the entire palp. These novel behaviors suggest that mate plugging and the eunuch phenomenon are more plastic repertoires than hitherto thought, and thus our observations add to possible pathways leading to them. Based on our examination of 791 samples of Nephilengys spp. from museum collections and of a freshly collected representative sample of N. borbonica, we conclude that i) palpal severance is common (50% of males from the wild were eunuchs lacking both palps), but ii) the females (or perhaps subsequent males) must possess a mechanism for removing severed palps from the epigyna (none had a whole palpal bulb), leaving behind only partial, embolic plugs, and iii) the disparity between male palpal damage (50%) and visible mating plugs in females (21%) merits further research as the relative numbers of severed males and plugged females can offer insight into which sex may have the upper hand in an evolutionary arms race.

Eight spider species of the genus Coelotes from Central Asia and the Near East currently assigned to the charitonovi species group are described. Four species, Coelotes charitonovi Spassky 1939, C. juglandicola Ovtchinnikov 1984, C. nenilini Ovtchinnikov 1999, and C. turkestanicus Ovtchinnikov 1999 are previously known from both sexes, and four others, C. caudatus de Blauwe 1973, C. arganoi Brignoli 1978, C. coenobita Brignoli 1978, and C. vignai Brignoli 1978 are known only from females. The dorsal views of the epigynum of C. juglandicola, C. caudatus, and C. vignai are illustrated and described for the first time.

This study analyzes predation by adult females of Misumenops pallidus (Keyserling 1880) on pairs of prey items representing non-pest insects and potential pests. The phenology of the potential pests was such that each insect guild peaked sequentially, while non-pest herbivorous and insectivorous insects were present during the entire period. Field experiments were made in a commercial 50-ha soybean plot during two successive years. Ten cages 1 × 1 × 0.5 m were placed in peripheral furrows of a soybean commercial plot. The pest species were preyed on differentially, with the order from the most favored species to the least with respect to non-pest herbivorous and insectivorous insects was as follows: defoliating lepidopterous larvae, seed feeding pentatomids in their early nymphal instars, stem boring lepidopterous larvae, and seed feeding pentatomids in older nymphal and adult instars. Adult females of M. pallidus fed on all the insect species offered, but in the presence of defoliator larvae, they hardly accepted alternative prey, whereas in the presence of other prey, they maintained a more generalized diet.

The karyotypes and course of meiosis of two pseudoscorpions, Semeiochernes armiger (Balzan 1892) and Cordylochernes scorpioides (Linnaeus 1758) (Pseudoscorpiones: Chernetidae), are described for the first time. The diploid chromosome number of the male is 69 in S. armiger and 47 in C. scorpioides. As in most pseudoscorpions studied to date, autosomes exhibit predominantly biarmed morphology. Both species possess an X0 sex chromosome system. In most pseudoscorpions with X0 system karyotyped so far, including European chernetids, the X chromosome exhibits metacentric morphology. In contrast, the X chromosome of both neotropical chernetids studied exhibits asymmetric, submetacentric morphology.

The tarantula genus Ephebopus is exceptional with respect to its urticating hairs: they are located on the palps rather than on the abdomen, as is the rule for other Neotropical tarantulas. These urticating hairs occupy a small field of 1–2 mm² on the medial side of the palpal femora. Each urticating hair measures 500–600 µm in length and 5–6 µm in diameter. Almost the entire hair shaft is studded with little barbs that point toward the hair tip. Urticating hairs arise from a slipper-shaped socket in the cuticle, at an angle of 25–30°. When the spider is threatened, it shows a brief palpal flick as a defensive reaction, whereby many urticating hairs are brushed off and fly through the air. These hairs do not have a preformed breaking point but become detached at the very base and are then pulled out from their sockets, like an arrow from a quiver. The actual release behavior occurs too quickly (0.1 s) to be followed by the naked eye. Video film analyses reveal that a single upward movement of the palps rubbing against the lateral surfaces of the spread chelicerae causes the dispersal of urticating hairs into the air.

When species with similar morphological and ecological characteristics occupy the same habitat, selection should minimize resource competition and promote coexistence by means of spatial partitioning. Competing species might exploit resources at different times or specialize in distinct resources. From July 2005 through May 2006 we examined the niche axes of two endemic sympatric desert species, Syspira tigrina Simon 1885 and Syspira longipes Simon 1885 in the State of Baja California Sur, looking for evidence that coexistence is fostered by differences in choice of microhabitat, temporal activity, occupation of space, or size. The results show high monthly microhabitat overlap (> 0.9). However, we found subtle differences in temporal activity and marked differences in juvenile and male body size, as well as some evidence of mutual spatial segregation. We conclude that body size and spatial segregation appear to be the dominant niche axes that facilitate coexistence of these species.

In this paper, we describe the construction and function of the double sheet and tangle web of Tidarren sisyphoides (Walckenaer 1842). Web construction includes several stages: construction of the scaffolding that serves to support the rest of the web; filling in the dome-shaped and horizontal sheets; and construction of the upper tangle. During construction of the scaffolding, the spider descends by a pre-existing thread to the substrate, moves a few centimeters and attaches the dragline, then she ascends by the new thread, doubling the line or attaching it to another thread. The spider fills in the sheet while walking in an irregular pattern under the sheet, and attaching her dragline using either one or both legs IV simultaneously to hold pre-existing sheet lines against her spinnerets. During scaffolding construction and filling in the dome-shaped sheet, the spider returns frequently to the retreat, apparently using the same threads near the retreat each time. Threads of both the dome-shaped sheet and the horizontal sheet have small drops of viscid material. The dome-shaped sheet and upper tangle comprise the functional trap of the web, while the horizontal sheet apparently plays only a little role in prey capture.

The ability to distinguish fossil arthropod carcasses from their molts is necessary for a more complete understanding of the arthropod fossil record and for more accurately assessing the role of fossil arthropods in paleoecosystems. Taphonomic characteristics, e.g., recurrent patterns of disarticulation of exoskeletal elements, are the primary data that have been used to differentiate fossil exuvia and fossil carcasses among arthropods. This study documents recurrent taphonomic patterns in modern scorpion carcasses and molts and extends these patterns to the fossil record to define criteria by which fossil scorpion molts might be distinguished from fossil scorpion carcasses. The three most useful and statistically significant characters in making the scorpion carcass/molt distinction are: position of the chelicerae (drawn in or extended); position of walking legs (folded or splayed); and body line (straight or curved). Two other characteristics, the position of pedipalps and presence or absence of telescoped segments, approach statistical significance and are also potentially useful. Disarticulation data are not as useful for distinguishing fossil scorpion molts and carcasses, because there are no statistically significant differences in length of time to total disarticulation or in the sequence of disarticulation between scorpion molts and carcasses. Among extant arthropods, scorpions possess the body plan most similar to that of the extinct eurypterids. Therefore, the taphonomic criteria developed for distinguishing fossil scorpion molts and carcasses may have implications for understanding molting among eurypterids.

Temperature can profoundly affect many physiological processes, including muscle performance. Many ectotherms appear sensitive to this relationship, choosing times and locations of activity permitting high body temperatures and, thus, quick escape from predators. High body temperatures, however, can lead to dehydration, which in turn affects muscle performance. Striped bark scorpions Centruroides vittatus Say 1821 provide an ideal model for assessing the effects of temperature and water loss on two potentially important antipredator behaviors, sprinting and stinging. Scorpions had significantly higher sprint speeds at warmer temperatures, with males significantly faster than females. Additionally, sting latency was longer and sting rate lower when scorpions were cooler. Intriguingly, females appear capable of stinging at a higher rate than males. Desiccation allowed the scorpions to sprint significantly faster than control (hydrated) scorpions, probably due to weight loss. The influence of temperature on sprinting and stinging might thus explain bark scorpions' preference for maintaining high body temperatures during periods when they are exposed to predation. When inactive, however, scorpions may benefit from maintaining lower body temperatures to decrease resting metabolic rate and desiccation.

Meiotic studies on three phylogenetically distant species of the genus Brachistosternus Pocock from Argentina were conducted. One species is from the subgenus Ministernus Francke 1985, B. ferrugineus Thorell 1876, and two species are from the subgenus Brachistosternus Pocock 1893, B. montanus Roig-Alsina 1977 (Andean species group), and morphologically different populations of B. pentheri Mello-Leitão 1931 (plains species group). All species showed achiasmatic meiosis, absence of heteromorphic bivalents, and bibrachial and monobrachial chromosomes of different sizes. Males of Brachistosternus ferrugineus, B. montanus, and one population of B. pentheri have 2n  =  46. Males of the typical populations of B. pentheri have 2n  =  42. These results suggest that B. pentheri may comprise two species.

Plesiochactas mitchelli Soleglad 1976 was originally described from a juvenile female collected in “Guatemala” before 1902. The species is redescribed on the basis of an adult female from a specific locality in the state of Chiapas; it is the first record of this species from México.

New data on the distribution and systematics of Patagonian species of the scorpion genus Urophonius Pocock 1893 are provided. A species of this genus from Península Valdés in central eastern Argentinean Patagonia, Urophonius martinezi new species, is described. The surface activity period of most of the species of the genus is reviewed and clearly established. A distribution map as well as a key for the Patagonian species of the genus are provided.

We conducted a field study in September 2007 and 2008 to analyze the foraging activity, natural diets, and predatory efficacy of Tetragnatha javana (Thorell 1890) (Araneae: Tetragnathidae) and Neoscona theis (Walckenaer 1842) (Araneae: Araneidae) on selected prey. The relationship between body measurements (carapace width, leg length, total body length, and body weight) and web dimensions (capture area, capture thread length, number of radii, number of spirals, and mesh height) of both species was also investigated. Most of the observed T. javana constructed their webs between two adjacent rice plants, while N. theis placed theirs at the top of rice plants. Both species required approximately an hour to complete a web, which differed significantly from each other in height, diameter, and capture area. Both species constructed only a single web per day. Web building activity of both species was intense from 17:00 to 18:00, while prey-handling activity was high from 19:00 to 20:00. In both species, peaks of feeding were recorded just after the peaks of prey handling (21:00). The main prey orders caught in the webs of both species were Lepidoptera, Diptera, Homoptera, Coleoptera, Hymenoptera, and Orthoptera. The time required to reach and capture lepidopteran (adults of stem borer and leaf folder) and homopteran prey was similar for both species. However, the time required to reach and capture orthopteran (grasshopper nymphs) prey was significantly longer for T. javana than for N. theis. Capture area increased with carapace width, and capture thread length increased with carapace width and body weight, while leg length and body length did not relate to either of these web variables. The number of radii, number of spirals, and mesh height did not correlate with any of the body size measurements. We concluded that both species can be used effectively to reduce insect pests of rice fields.

Several spider species use plants as shelter and foraging sites, but the relationships among these organisms are still poorly known. Lynx spiders of the genus Peucetia do not build webs, and many species live strictly in plants bearing glandular trichomes. Peucetia flava Keyserling 1877 inhabits Solanum thomasiifolium in southeastern Brazil and usually preys on herbivores and other small insects adhered to the glandular trichomes of its host plant. To evaluate the potential anti-herbivore protection of this spider species for S. thomasiifolium, we glued termites used as herbivore models on trichomes of S. thomasiifolium and on neighboring plants lacking glandular trichomes. Leaf miner damage and spider density were recorded for S. thomasiifolium plants in July 1997. There was a positive relationship between plant size and spider density. The removal of termites in S. thomasiifolium by P. flava was higher than in plants without glandular trichomes. The leaf miner damage was negatively related to spider density. Our results suggest that P. flava may be an important plant bodyguard in the defense of S. thomasiifolium from its natural herbivores.

A simple technique is presented for reducing the fluorescence of living scorpions by prolonged exposure to UV light. Scorpion's fluorescence peak can be eliminated by a 1-mo exposure to low intensity UV light. Although the fluorescence peak returns within 1 wk after removal from UV light exposure, the magnitude remains reduced. This technique potentially opens up new options for testing a variety of hypotheses about possible functions of scorpion fluorescence including potential effects on cuticle strength, visual responses, predation, cannibalism, and mating.

Reports of scorpions on epiphytic bromeliads in temperate forests are scarce. Here we present some ecological aspects of this animal-plant interaction in three different types of temperate forests (pine, pine-oak and oak forest) in Oaxaca, Mexico. From 2005 to 2007, we collected 373 bromeliads belonging to 10 species, and each plant was defoliated in search of scorpions. We found 35 individuals of Vaejovis franckei Sissom 1989 in 19 bromeliads: 22 specimens in Tillandsia carlos-hankii with 21% occupancy and an average abundance of 2.1 ± 1.9 individuals/plant; 12 specimens in T. prodigiosa (10% occupancy, average abundance  =  1.6 ± 0.6) and one specimen in T. calothyrsus (3% occupancy, average abundance  =  1 ± 0.0). Pine-oak forest had 29 individuals; pine forest, 4 individuals; and oak forest, 2 individuals. Percentage of occupancy differed among localities, while average abundance remained the same. Vaejovis franckei preferred T. carlos-hankii and pine-oak forest, which was correlated with the percentage of occupancy but not with the average abundance.

Microfilistata ovchinnikovi new species (Araneae: Filistatidae), the second member of this formerly monotypic Central Asian genus, is described from Kyzyl-Dzhar Ravine, Southern Turkmenistan. The genus is redescribed and referred to the Filistatidae insertae sedis.

In the green lynx spider Peucetia viridans (Hentz 1832), the two openings of a mated female's epigynum are often sealed by copulatory plugs, sometimes with the two-pronged distal portion of the paracybium of a male palpus inserted in each opening and embedded in the plugs. The presence of copulatory plugs and paracymbia may prevent further mating by the female. However, not all mated females exhibit these structures, perhaps allowing some P. viridans females to mate with more than one male, despite the assertion of Whitcomb & Eason (1965) that females only mate once. We investigated this possibility by surveying the extent of multiple paternity in field-collected P. viridans broods from southern California. For adult females and their egg sacs, we determined the aspartate aminotransferase genotype for each mother and her spiderlings using allozyme electrophoresis in order to assess whether the progeny data best fit with a single male as the father. Two broods exhibited clear evidence of multiple paternity, verifying that multiple mating by females is possible in this species. Although most mothers of single paternity broods had one or both epigynal orifices blocked, some had no blockage at all, while the two mothers of multiple paternity broods had some kind of blockage to one or both orifices, suggesting that neither plugs nor inserted paracymbial processes are associated with a reduction in female remating.

All scorpions possess jointed, ventral appendages called pectines. These organs have chemosensory, peg-shaped sensilla that detect substrate-borne chemicals. Previous physiological studies show that neurons within peg sensilla respond to an assortment of volatile organic chemical stimulants blown across the sensillar opening. We developed an improved method of chemical stimulant delivery called the mineral oil flood technique to further investigate the neural circuitry of scorpion pectines. The new mineral oil flood technique allows us to deliver chemical stimulants directly to individual sensilla by introducing a polar, liquid substance under non-polar mineral oil. Unlike previous methods of stimulant delivery, the mineral oil flood technique allows for precise control over the duration of direct contact between a liquid stimulant of known concentration and a sensillum.

I describe the female and redescribe the male of Theridion italiense Wunderlich 1995 from live and alcohol-preserved material and provide notes on the ecology, distribution, and affiliations with the very similar Theridion uhligi Martin 1974 and Theridion petraeum L. Koch, 1872.

Zodariellum asiaticum (Tyschchenko 1970) is an ant-eating spider from Central Asia. Using five syntopically occurring ant species, namely Cataglyphis aenescens, Formica cunicularia (both Formicinae), Messor aralocaspius, Tetramorium caespitum (both Myrmicinae), and Tapinoma erraticum (Dolichoderinae) in a laboratory study of prey-capture behavior, I evaluated capture frequency, attack latency, number of attacks, and paralysis latency. Although spiders captured all five ant species, capture efficiency varied when spiders were tested with the different ant species, being highest when the spiders were tested with F. cunicularia. I concluded that small juvenile Z. asiaticum probably adapt to feed primarily on species of small dolichoderine and myrmicine ants and that large juvenile and the adult Z. asiaticum adapt to feed primarily on large formicine ants.