The new species Brachistosternus paulae is described. This is the southernmost species of the genus, occurring in southern Patagonia in Santa Cruz Province. It can be distinguished from all the other species of the genus by the presence of only 4 ventral trichobothria on the pedipalpal chela, and by the shape of the hemispermatophore, in which the cylindrical apophysis is shorter than the laminar apophysis; all internal spines are absent, except for the row of spines, which in some specimens is vestigial. This species can not be included in any of the known subgenera due to its trichobothrial pattern; nevertheless it is closer to the subgenus Leptosternus on the basis of its remaining morphology. A key for the species of the genus in the country is provided together with some data on them. The hemispermatophores of the three subgenera are compared and two maps detailing the distribution of the species in the country are provided.

El género Brachistosternus en la Argentina, con la descripción de una nueva especie de la Patagonia (Scorpiones, Bothriuridae). En este trabajo se describe a Brachistosternus paulae n. sp. Esta es la especie conocida más austral del género, habitando en el sur de la Patagonia en la provincia de Santa Cruz. Puede diferenciarse del resto de las especies del género por la presencia de solo 4 tricobotrias ventrales en la pinza y por el escaso desarrollo de su hemiespermatóforo, en éste la apófisis cilíndrica se encuentra poco desarrollada y es más corta que la apófisis laminar, además carece de todos los procesos espiniformes, salvo las espinas en hilera que en algunos ejemplares pueden presentarse en forma vestigial; la particular tricobotriotaxia de esta especie no permite incluirla en ninguno de los subgéneros descriptos hasta el momento, sin embargo su morfología la aproxima más al subgénero Leptosternus. Se presenta además una clave para las especies del género en el país y se aportan algunos datos sobre éstas. Se comparan los hemiespermatóforos de los distintos subgéneros y se presentan dos mapas con la distribución de las distintas especies presentes en el país.

Patterns of growth, phenology and reproduction were studied in a field population of the wolf spider Pirata piraticus from November 1997 until October 1998 and in June 1999 to unravel the intrapopulation variation and co-variation of these traits. Individuals of P. piraticus overwinter as juveniles of different instars while adults were found from the end of April until September. Strong year to year variation in the age and size of overwintering juveniles was present, resulting in a corresponding difference in adult size in the subsequent breeding season. The main period of reproduction occurred from May until August with larger individuals breeding earlier in the season. The size at which adults breed was also significantly different in the successive years. Clutch mass (cocoon mass), clutch volume and fecundity are dependent on the size of the female according to a weakly negative allometric relationship. The differences in those reproductive traits between the succesive years are therefore proportionate to the differences in female size. This was in clear contrast to egg size, a life history trait that shows much less variation and appears to be independent of female size. Therefore, egg size was not significantly different between spring 1998 and spring 1999. There is, however, some variation in fecundity due to egg size and number independent of female size. When corrected for female size, females with larger eggs produce relatively fewer eggs indicating a trade-off between these two reproductive characters.

The females of Anapis castilla Platnick & Shadab from the state of Amazonas and Anapisona bordeaux Platnick & Shadab from the state of Rio Grande do Sul both in Brazil, are described.

Most adult golden orb weavers (Nephila clavipes) have kleptoparasites of the genus Argyrodes in their webs. The kleptoparasitic load correlates positively with web size. Clustered (interconnected) webs have a more predictable number of kleptoparasites than do solitary webs, but there is no difference in the mean number of kleptoparasites between the two. From the view of the kleptoparasite, host webs are habitat patches or islands. Isolated webs show characteristics of small patches, where web size is a poor indicator of kleptoparasite number and variation is high. The distribution of kleptoparasites in clustered webs, on the other hand, seems to fit the “ideal free distribution” where web size nearly entirely predicts kleptoparasitic load. Thus clustered webs, as a habitat patch, are more than merely the combination of their parts. The predictability of kleptoparasite load in clustered webs may be a function of the stability (longevity) of those habitat patches, and ease of colonization, as neighboring webs act as sources.

The purpose of this study was to identify spiders associated with foliage of sugar maple, Acer saccharum Marsh. and white ash, Fraxinus americana L., and to investigate their distribution and relative abundance within the crowns of these two northern hardwoods. Spiders were collected during June through August 1995 from the lower and mid-crowns of ten dominant/codominant sugar maples, five white ash and understory sapling and herbaceous foliage ≤2 m from the ground in a northern hardwood stand in Cortland County New York. These samples were compared for differences in species composition and density (number/25 leaf-clusters; number/100 g dry leaf weight). The spider fauna obtained from this intensive sample was compared to that of an extensive, 20-year survey from the mid-crown of sugar maple in 15 northern hardwood stands in northern New York (St. Lawrence and Lewis Counties). The intensive overstory collection (1995) from maple provided 694 specimens (7 families, 11 genera, 13 species). The dominant families were Philodromidae (43%) and Theridiidae (26%). The most abundant species were Philodromus rufus Walckenaer 1826 and Enoplognatha ovata (Clerck 1757). Sugar maple averaged 2.6 ± 0.6 spiders/25 leaf-clusters and 14.2 ± 0.6/100 g of foliage. Density of dominant taxa and total numbers did not differ significantly (α = 0.05) between crown positions. Significantly fewer hunters/100 g leaf weight occurred on the distal half of mid-crown branches compared to the basal half. Hunters were the dominant foraging guild in terms of both numbers (65%) and number/100 g leaf weight (56%). One hundred twenty four specimens were obtained from white ash (7 families, 9 genera, 9 species). Density on ash averaged 2.6 ± 1.3/100 g leaf weight and P. rufus and Araniella displicata (Hentz 1847) were the most abundant species. Significantly fewer spiders occurred on white ash compared to sugar maple (14.2 ± 0.6/100 g of foliage. The extensive sample provided 712 specimens consisting of 12 families, 27 genera and 40 species. The most abundant species recovered was Pelegrina proterva (Walckenaer 1837). The web spinner, E. ovata was the most common species recovered from understory foliage (96% of 763 specimens).

The male of Xysticus brevidentatus Wunderlich 1995 was originally described from Dubrovnik in Croatia, but females have remained unknown. During a revision of museum material in Vienna further specimens including both males and associated females from Albania, Italy and Yugoslavia were discovered. The morphology of the male pedipalp allows the placement of X. brevidentatus in the cristatus group which contains, among others, X. cristatus (Clerck 1757), X. audax (Schrank 1803), X. macedonicus Šilhavý 1944 and X. pseudocristatus Azarkina & Logunov 2001. Detailed analyses of the females showed that the shape of the female epigyne and vulva is consistent with the general scheme of the cristatus group and that the specimens can, due to a number of distinctive characters, be regarded as the females of X. brevidentatus.

The first fossil cyphophthalmid harvestman, Siro platypedibus new species (Arachnida, Opiliones, Cyphophthalmi), is described from Bitterfeld amber, Sachsen-Anhalt, Germany. The age of this amber is in dispute. Geological studies support a Miocene (20–22 Ma) date for the deposit, but the presence of insect species identical to those in Baltic amber (dated at ca. 35–40 Ma) has led other authors to suggest that the Bitterfeld amber comprises older, redeposited material, contemporary with Baltic inclusions. Two features in this harvestman fossil are consistent with the Recent genera Siro, Paramiopsalis and Tranteeva: (a) smooth tarsi and metatarsi in legs 1 and 2 and (b) the apparent absence of a dorsal crest on the basal article of the chelicera. Unequivocal autapomorphies of any one of these genera are not clearly preserved in this fossil, but Paramiopsalis is a monotypic Iberian genus, and Tranteeva is a monotypic genus from Bulgaria, while Siro is more diverse and widely distributed, including living representatives in Central Europe relatively close to the Bitterfeld type locality. For this reason we assign the fossil to Siro.

Competition among males is a major force shaping sexual selection. We investigated the male mating strategy of the widow spider Latrodectus revivensis, a desert species with an annual life cycle. Based on morphology of the sperm storage organs reported for female Latrodectus, we predicted that males should guard sub-adult or virgin adult females. In a natural population, we found that males were generally monogamous, cohabiting longer with sub-adult females approaching the final molt than with adult females. Nevertheless, both the duration and timing of male cohabitation were highly variable. Males were found with females from a few days before or after female maturation to over two months after maturation. Maturation of males and females peaked in spring, with a second, smaller peak in summer. Adult males that matured in spring were larger than those maturing later in the summer, while for adult females the pattern was reversed. We suggest that large males of L. revivensis that mature in spring maximize reproductive success by mating with virgins. Late males will gain greater reproductive success from mating with large, late-maturing females, but the scarcity of these females in the population at this season may make opportunistic mating with non-virgin females a viable strategy.

Guasinia persephone, a new species of the family Guasiniidae, is described from the soil of an inundation forest in Brazilian Amazonia. This family was hitherto only known from two species from Venezuela. Male genitalia of the new species are described in detail. A close relationship of Guasiniidae with Zalmoxidae and Fissiphalliidae is proposed on basis of genital morphology. This is the third species of blind Laniatores from Brazil and the first from leaf mold, one is from termite nests and the other is from a cave.

The genus Lyssomanes (Salticidae) is recorded and described from a fossil in 20–30 Ma Oligocene–Miocene amber from Chiapas, Mexico for the first time. This is the oldest described Lyssomanes and extends the known geological range of the genus by approximately 10 Ma from the previously oldest known specimens in Dominican Republic amber. The geological age of the family may be young compared to other extant spider families.

RESUMEN. El genero Lyssomanes (Salticidae) es descrito y registrado por primera vez incluido en el ámbar de Chiapas, México, tomando en cuenta una edad de 20 a 30 Ma (Oligoceno-Mioceno). Éste es el registro más antiguo que se tienen de Lyssomanes y con esto se extiende el rango geológico conocido para el género por aproximadamente 10 Ma de los especimenes previamente conocidos y más antiguos del ámbar de la Republica Dominicana. Geológicamente la edad la familia puede ser joven comparado con otras familias existentes de arañas.

Magnetic heading (direction the spider's ventrum faced) and web inclination (degree of slant from the vertical) in Argiope trifasciata Forskål, a diurnal orb-weaving spider, were studied at a coastal site in southern California for nine weeks in fall 1999. Throughout the study, A. trifasciata largely occupied east-west oriented webs with their venters facing south and southwest. Mean magnetic heading was unaffected by ambient temperature extremes. Inclination levels varied from week to week over an approximately 5° range. However, these changes followed no discernible pattern and were independent both of the sun's decrease in maximum altitude during the course of the study and of magnetic heading. Since the ventrum of A. trifasciata is dark, the consistent southern orientation exhibited by spiders at our study site suggests that they sought to maximize solar radiation in an attempt to gain heat. In addition, the east-west, facing-the-sun orientation of webs at this site places them parallel to the prevailing western breezes, minimizing their exposure to wind disturbance. As for inclination, it is unclear what factors may be influencing the degree of slant in A. trifasciata webs and further study will be needed to ascertain what they might be.

The first molecular phylogeny is presented for four species of the scorpion genus Mesobuthus, based on DNA sequences of three gene fragments (two mitochondrial and one nuclear protein coding gene, ∼1 kb). The inferred phylogeny based on a pooled maximum likelihood analysis revealed a clear deep splitting between the “western clade” consisting of M. gibbosus and M. cyprius (Greece/Anatolia, Cyprus) and the “eastern clade” consisting of M. eupeus and M. caucasicus (Anatolia/Central Asia). The species M. caucasicus (recently placed in the genus Olivierus Farzanpay 1987) groups monophyletically within Mesobuthus; thus, the genus Olivierus is synonymized here with Mesobuthus. Sequences of M. eupeus and M. caucasicus sampled mainly from Kazakhstan and Uzbekistan are highly structured, indicating the possible existence of multiple species.

Major ampullate (dragline) silk is attracting significant attention as a potentially useful engineering fiber. This interest is motivated by reports that the silk exhibits high mean strength, stiffness and toughness as measured in tensile tests. However, the typical testing conditions (constant strain rate; experiment completed within less than an hour) imposed during such assessments do not reflect typical demands (e.g. ability to support constant load for long times) made on real high-tensile materials. We demonstrate here that Nephila clavipes major ampullate silk subjected to constant loads performs poorly: its breaking strength is significantly lower than that measured in conventional constant strain rate tests, and even very small constant loads can cause elongation to increase appreciably over long timescales.

Foraging behavior in spiders can be influenced by a variety of factors. Here we investigate the effects of hunger and predation risk on feeding behavior in the wolf spider Pardosa milvina (Hentz 1877) (Araneae, Lycosidae). Pardosa milvina is preyed upon by the larger wolf spider, Hogna helluo (Walckenaer 1837), and responds with appropriate antipredator behavior to the silk and feces of this species. We predicted that hungry Pardosa milvina would be more likely to forage and consume prey under predation risk than satiated individuals. We found that hungry Pardosa under predation risk consumed as many prey as spiders not under predation risk. However, satiated Pardosa consumed significantly fewer prey when under predation risk. Our data suggest that the animal's energetic needs are weighed against the risks of foraging when predators may be present.

Pisaurids such as Dolomedes triton (Walckenaer 1837) are well known as inhabitants of ponds and streams and are adept at locomotion on the water surface. In a broad survey of water surface locomotion in spiders, we have found that most taxa do not use specialized gaits under these circumstances. However, some tetragnathids, araneids, and salticids (three families that are outside of the superfamily Lycosoidea to which the pisaurids belong) resemble D. triton to the extent that they do use specialized gaits when on the water surface. Of these, the tetragnathids are particularly accomplished at water surface locomotion, achieving velocities that exceed those of D. triton when it rows, but not when it gallops.

Observations on the wolf spider Schizocosa mccooki in northern California grasslands reveal previously unreported burrowing behavior, known to occur in only one other member of the genus. Adult and penultimate female S. mccooki may occupy burrows that vary widely in depth and the occurrence of silk linings. Mark-resight techniques revealed burrow fidelity spanning several weeks for individual spiders. Behaviors such as courtship and prey consumption can occur at, but are not restricted to, the entrances to these burrows. Burrows appear to offer daytime shelter for S. mccooki, though it remains unclear whether protection from predators or amelioration of abiotic conditions is the primary basis for burrow use.

Little information is available concerning the tree species preferred by the American red-legged purseweb spider, Sphodros rufipes (Latreille 1829), for supporting their webs. During a study of the spiders of northwestern Louisiana, 26 pursewebs of S. rufipes were found. All were on deciduous trees, with 58% found on sweetgum or oak. None of the webs were on conifers or herbaceous plants even though conifers made up 7–92% of the trees in the sampled areas. All pursewebs were within 20 m of a stream and were on trees with a trunk less than 70 cm dbh.

Males of the Neotropical harvestman Ampheres leucopheus (Mello-Leitão 1922) were observed guarding egg-batches attached to the undersurface of leaves. As recorded for other paternal harvestmen, males of A. leucopheus guard egg-batches containing eggs in different developmental stages as well as newly hatched nymphs. This is the second case of paternal care recorded among gonyleptids and the fifth in the order Opiliones.

Copulatory behavior of Tidarren sisyphoides is described for the first time. Courtship proceeds without construction of a mating thread. The male dies during insertion and remains coupled to the female epigynum for 2.4 hours on average (n = 15). In contrast to other species hitherto studied, females of T. sisyphoides do not consume their mates after copulation. Instead, the dead males are removed from the webs by the females.