A new Stylocellus from Singapore, the smallest species of the genus, is described and fully illustrated. The family Stylocellidae is rediagnosed and emended to include the representatives of the genera Miopsalis and Fangensis based on the results of a phylogenetic analysis of the cyphophthalmid genera (Giribet & Boyer 2002).

Cribellar threads are primitive prey capture threads formed of thousands of fine, looped cribellar fibrils that surround larger, supporting fibers. Cribellar fibrils are produced from the spigots of an abdominal spinning field, the cribellum, which may be either a single, oval plate or a pair of medially divided plates. The number of spigots on a spider's cribellum is known to be directly related to the stickiness of its cribellar thread. Some spiders deposit cribellar threads in their webs as taut, self-supporting linear threads; others deposit looped threads along a supporting foundation thread. This study showed that the looped cribellar threads of Kukulcania hibernalis (Filistatidae) and Mexitlia trivittata (Dictynidae) were wider and stickier than linear threads produced by Waitkera waitakerensis and Uloborus glomosus (Uloboridae), respectively, that had the same numbers of cribellum spigots. Linear cribellar thread spun from the divided cribellum of K. hibernalis was both wider and stickier than linear thread spun from the undivided cribellum of W. waitakerensis that had the same number of spigots. A single cribellar plate of K. hibernalis and the cribellum of Siratoba referena (Uloboridae) had a similar number of spigots and produced cribellar threads with similar stickiness. Thus, both a spider's spinning anatomy and its spinning behavior affect the stickiness of its cribellar threads.

The mate preference characteristics of adult Tetragnatha elongata were assessed with respect to measures of female mass, linear size (length), and condition (mass scaled by length: body condition). Males preferred longer, heavier females and females with higher body condition indices. When mass is partially controlled, males still preferred females of higher body condition, but reversed their preference for length and chose smaller females. We present evidence that female body condition and mass are associated with the volume of her egg load and the proximity of oviposition, whereas female body length is not associated with either. Females displayed no clear preference among males for mass or linear size, but were reluctant to mate in female-choice trials. The small sample size obtained may have obscured the detection of female mate preferences if they exist. This may be the first evidence that mate choice is influenced by body condition rather than mass or linear size among spiders.

Kleptoparasitic spiders are known to have a close association with host spiders, yet there have been few studies demonstrating how host availability influences the dynamics of kleptoparasites. Field surveys were conducted at five sites differing in host composition in sub-tropical areas in Japan, at about two-months intervals. Argyrodes flavescens and A. bonadea were both found more frequently on webs of two Nephila species than expected from the web areas they occupied among webs of all web spiders. Seasonal dynamics of Argyrodes changed greatly according to whether N. clavata was present or not, indicating the importance of Nephila on Argyrodes populations. The peak density of A. bonadea came earlier than that of A. flavescens. Because A. flavescens is known to limit the number of A. bonadea on host webs, the decrease in the density of A. bonadea may be due to the effect of interspecific competition by A. flavescens.

Stegodyphus mimosarum of the African savanna form communal nests consisting of few to several hundred individuals and co-operate in nest construction and maintenance, brood care and prey capture. We tested large and small individuals for differential responses to different prey risk types. To date, there has been no conclusive evidence of tasking in these or other social spiders. If tasking occurs, small spiders should approach and attempt to subdue less dangerous prey items such as flies more often than the more dangerous prey items such as bees. Hungry individuals were significantly more willing to venture out of the nest refuge and thus accept the costs associated with prey capture than were satiated spiders. Apparent depletion of poison in previous prey captures did not significantly affect an individual's response to a prey item. Spiders treated more dangerous prey (bees) more carefully than less dangerous prey (flies), but there was no difference in the response of large versus small spiders to prey. The two-way interaction between spider size and prey type was never statistically significant, indicating a lack of tasking in this species.

The spermatogenesis of four species of haplogyne spiders from Argentina is analyzed. Dysdera crocota (Dysderidae) (n = 5 X0) has holokinetic chromosomes, achiasmatic male meiosis and a post-reductional division of the sex chromosome. Ariadna boesenbergii (Segestriidae) (n = 4 X0) also possesses holokinetic chromosomes, but meiosis is chiasmatic and the X chromosome divides pre-reductionally. Kukulcania hibernalis (Filistatidae) (n = 11 X₁X₂0) and Scytodes globula (Scytodidae) (n = 6 X0) have metacentric and submetacentric chromosomes, chiasmatic meiosis and the sex chromosomes divide pre-reductionally. Kukulcania hibernalis possesses a bimodal karyotype and a particular chromatin coiling during prophase I, while Scytodes globula has striking proximal localization of chiasmata. These results show that Haplogynae present high cytogenetic heterogeneity: species with holokinetic chromosomes as well as species with monocentric chromosomes (metacentric and submetacentric), and species with low diploid numbers, achiasmatic meiosis and proximal chiasma localization.

Many species of spider disperse by ballooning (aerial dispersal), and indices of aerial activity are required in studies of population dynamics and biological control in field crops where spider immigrants are needed for pest suppression. Current methods (e.g., suction traps, sticky traps, deposition traps) of monitoring aerial activity are very labor-intensive, expensive, or require a power supply. We tested Ballooning Index (BI), an alternative, simple method utilizing inexpensive equipment. This method involved the monitoring of spiders climbing an array of 30 cm tall wooden sticks placed vertically in short turf. During a two-year study in arable land in the UK, the incidence of spiders (mainly Linyphiidae) on sticks was correlated with the numbers caught at 1.4 m and 12.2 m above ground in suction traps. Climbing activity on sticks was greater during the morning than in the afternoon, and this activity started progressively earlier in summer than in winter. There was no seasonal change in the proportion of spiders caught at the two heights in suction traps. The pattern of catches (on sticks and in suction traps) suggested strongly that the majority of ballooning spiders dispersed by a number of short flights, rather than by a single long flight, and that segregation of immigrants and emigrants is not possible by any current method. The BI method appears to be, however, a simple and reliable technique for monitoring the overall aerial activity of ballooning spiders.

In Denmark, two seemingly distinct size-classes, 3^rd and 4^th instar juveniles and reproductive adults, of Araneus diadematus are found during every breeding season in autumn, indicating a non-overlapping biennial life-cycle. We tested the hypothesis that alternate generations might experience a degree of reproductive isolation, using the distribution of nuclear (allozyme) and maternal (mtDNA) genetic markers. Individuals of a locality behaved as belonging to a random mating population, irrespective of size. No differences were found between any size-class pairs, within and between 2 yr, or among geographically distant samples. Processes that may lead to this result are discussed: the biennial development may be incomplete; or there may be migrational influx of genes from southern annual populations. There is no evidence for sexual differences in life-cycle length.

We examined the utility of several popular formulae used to estimate the capture areas of orb webs across a large sample of Cyclosa Menge 1866 and Tetragnatha Latreille 1804 webs. All formulae evaluated contained at least some bias in estimation of the capture areas of webs. We identified two types of asymmetry in orb webs that affect capture area estimation differently. Web asymmetry measures the ratio of the horizontal and vertical diameters of orb webs while hub asymmetry measures the displacement of the hub from the geometric center of a web. An analysis of model webs that varied in web and hub asymmetry showed that most formulae overestimated capture area as web asymmetry increased and that some formulae also overestimated capture area as hub asymmetry increased. Only the “Ellipse−Hub” formula was unaffected by web and hub asymmetry. Although the “Adjusted Radii−Hub” formula provided a slightly more accurate overall estimate of capture area, we recommend that the “Ellipse−Hub” formula be used when comparisons of capture area are made between taxa or individuals that vary in web and hub asymmetry.

This paper presents the description of the new species, Acrographinotus mitmaj (Opiliones, Gonyleptidae, Pachylinae). It can be easily distinguished from its congeners by: male femur IV long and spiny, devoid of the rows of tubercles and/or apophyses characteristic of other nominal species in the genus; further, A. mitmaj new species bears a less developed median apophysis on the 3^rd free tergite (larger armature in other species). Penis morphology (especially concerning the ventral process of the stylus) agrees with the generic diagnosis. Known localities of the new species are restricted to the upper Río Cañete valley (Departamento Lima, central Peru).

Five new species of Solifugae are described from North America: Eremobates chihuaensis, Eremobates gerbae, Hemerotrecha sevilleta, Hemerotrecha cornuta, Eremochelis oregonensis as well as the females of Eremocosta gigasella (Muma, 1970), and Eremobates polhemusi Muma & Brookhart, 1988.

Orobothriurus atiquipa new species (Scorpiones, Bothriuridae) from Lomas formations in the coastal desert of southern Perú is described and illustrated. This species belongs to the alticola species-group, and within the group, it is closely related to O. alticola (Pocock), O. paessleri (Kraepelin) and O. curvidigitus (Kraepelin). The spine formula (4 3) on tarsi III–IV is probably an autapomorphy for the new species. Some features of the habitat (the Lomas formation are green isolates in the coastal desert), as well as a distribution map are provided.

RESUMEN. Se describe Orobothriurus atiquipa nueva especie de escorpión Bothriuridae, colectado en una formación de Lomas en el desierto costanero del Sur del Perú. Esta especie pertenece al grupo alticola; dentro de éste, las especies más próximas son O. alticola (Pocock), O. paessleri (Kraepelin) y O. curvidigitus (Kraepelin). La fórmula de espinulación tarsal en patas III–IV (4 3) es probablemente una autapomorfia de la nueva especie. Se presentan también algunos datos del habitat de O. atiquipa (las formaciones de Lomas son verdaderos parches de vegetación dentro del desierto costero), así como un mapa de distribución.

The species Metacleobis fulvipes Roewer 1934 (Solifugae, Mummuciidae), previously known only from the male holotype, is redescribed based on the holotype and other male and female specimens. Illustrations of the main diagnostic characters are provided, and new occurrences of this species in Brazil are reported. Some behavioral observations of one individual kept in a terrarium are given.

RESUMO.A espécie Metacleobis fulvipes Roewer 1934 (Solifugae, Mummuciidae), conhecida previamente apenas pelo holótipo macho, é redescrita a partir do holótipo e de outros exemplares machos e fêmeas. Ilustrações dos principais caracteres são fornecidas e novas ocorrências da espécie no Brasil são registradas. São descritas observações comportamentais feitas a partir de um indivíduo mantido em terrário.

A phylogenetic analysis of the genera of Cyphophthalmi is undertaken by studying 32 morphological characters in 43 species representing all families and most genera. The analysis is complemented with a molecular analysis using 18S rRNA and 28S rRNA sequence data of twelve cyphophthalmid species representing ten genera. The Cyphophthalmi are monophyletic, as are the families Stylocellidae and Pettalidae. However, the families Sironidae, Ogoveidae, and Neogoveidae are not monophyletic. Relationships among families need more data, but molecular characters strongly support the monophyly of Troglosironidae Neogoveidae. Rooting the cyphophthalmid tree by using sequence data of one Eupnoi, one Dyspnoi, and one Laniatores results in two alternatives, one proposing a sister group relationship of Stylocellidae to the remaining taxa, or alternatively Pettalidae (with Suzukielus?) as sister group of the remaining cyphophthalmids. The position of Troglosiro, Suzukielus, Metasiro, Huitaca, and the epigean “Neogovea” mexasca are re-evaluated and discussed.

The African spider genus Singafrotypa Benoit is redescribed and transferred from the tetragnathid subfamily Nephilinae to the araneid subfamily Araneinae. Cladistic analysis of the matrix of Scharff & Coddington (1997) with the addition of two Singafrotypa species supports this new placement. Singafrotypa acanthopus Simon, the type species of the genus, is described along with two new species: Singafrotypa okavango new species from Botswana, and Singafrotypa mandela new species from South Africa. Singafrotypa goliath Benoit is transferred to Neoscona Simon (Araneidae, Araneinae).

The copulatory organs of the cryptic species Lycosa thorelli and Lycosa carbonelli are studied and are shown to exhibit some differences. The morphology of the epigynum, vulva and palpal organs of L. carbonelli are here described for the first time. Additional morphological data of these species are provided and the specific diagnosis reformulated. Measurements indicated that the copulatory organs of L. carbonelli are larger than L. thorelli. Morphological comparison between the parental species and the hybrid progeny show that hybrids are intermediate in morphology and size. The reproductive isolation in these cryptic species and the inheritance of the sexual characters in the hybrid progeny are discussed.

We studied temporal variation in adult size and sexual size dimorphism (SSD) of seven hunting spider species, Ctenus amphora, C. crulsi, C. manauara, C. villasboasi (Ctenidae), Phoneutria fera, P. reidyi (Ctenidae), and Ancylometes rufus (Pisauridae) in a tropical rainforest, and one species from a relatively open vegetation habitat, C. minor, in central Amazonia. Size variation was great within and among field trips. Spiders were generally smaller in October (end of dry season) when compared with other months: adults of C. amphora, C. crulsi and C. manauara were significantly smaller in October 1995 when compared to February 1996; P. fera were smaller in October 1998 than in June 1998; and A. rufus were smaller in October 1998 than in August 1998. The temporal variation in size is possibly a result of low prey availability during the dry season. Six species had significant differences in prosoma length between males and females: C. amphora, C. crulsi, C. manauara and C. minor had larger males (which is considered rare in spiders), and P. reidyi and P. fera had larger females. However, considering an alternative index of size, the “rough area” (an approximate measure of the area of the spider as seen from above), the males were significantly larger for all species (up to 2.8 times in C. minor), because they have longer legs relative to their prosoma length. We suggest that selection for high mobility may be the reason for adult males with longer legs, and that the smaller species had higher degrees of sexual dimorphism in leg length because of the relative size of obstacles in the leaf litter.

RESUMO. Estudamos a variação temporal de tamanho de adultos e o dimorfismo sexual de tamanho de sete espécies simpátricas de aranhas errantes, Ctenus amphora, C. crulsi, C. manauara, C. villasboasi (Ctenidae), Phoneutria fera, P. reidyi (Ctenidae), e Ancylometes rufus (Pisauridae) em uma floresta tropical úmida, e uma espécie em um habitat de vegetação relativamente aberta, C. minor, na Amazônia Central. A variação de tamanho foi grande dentro e entre excursões de coleta. As aranhas foram geralmente menores em outubro (final da estação seca) comparado com outros meses: adultos de C. amphora, C. crulsi, C. manauara e C. minor foram significativamente menores em outubro de 1995 comparado a fevereiro de 1996: P. fera foram menores em outubro de 1998 do que em junho de 1998 e A. rufus foram menores em outubro de 1998 do que em agosto de 1998. A variação temporal em tamanhos observada é possivelmente um resultado de baixa disponibilidade de presas durante a estação seca. Seis espécies tiveram diferenças significativas em comprimento do cefalotórax entre machos e fêmeas, C. amphora,