The huntsman spider genus Vindullus Simon 1880 (Araneae, Sparassidae) is revised. Olios gracilipes Taczanowski 1872 is transferred to the genus and recognized as a senior synonym of the type species, Vindullus viridans Simon 1880, for which the former male syntype was designated as a lectotype. Vindullus kratochvili Caporiacco 1955 is placed as incertae sedis and four new species are described: Vindullus undulatus new species, Vindullus gibbosus new species, both from Peru and Vindullus angulatus new species, from Colombia and Venezuela and Vindullus concavus new species from Brazil.

Comb-hairs on the fourth tarsi of males and females are a classical theridioid character, but they also occur in pholcids. Previous studies on Pholcus phalangioides (Fuesslin 1775) have shown that in this species the comb-hairs function in the context of sticky silk wrap attack just as in theridiids. Here we investigate pholcid comb-hairs in a comparative way, studying the tarsal hairs of representatives of 42 pholcid genera with the SEM. We found two principal morphologies, a simple and a complex type of comb-hair. We found two principal types of comb-hair distribution on the tarsus: in distal patches or in ventral rows, but intermediate types also occur. Character mapping suggests that simple comb-hairs are derived from complex ones, and that distal patches are plesiomorphic, ventral rows derived. We speculate that pholcid comb-hairs may be derived from hairs (the “accessory claws”) that grasp silk in functional correlation with the median claw. In a female shock-frozen during wrap attack, the silk line passed through the notch of a comb-hair, but several functional details (silk grasping and releasing, function of different hair branches) remain unanswered.

A new genus of Amaurobiidae, Himalmartensus, is described from Nepal, and includes three species: the type species H. martensi new species, H. ausobskyi new species, and H. nepalensis new species. Members of this new genus can be separated from other amaurobiid genera by the combination of the following characters: the presence of a colulus, a single chilum, smooth trichobothrial bases, and simple tracheal tubes. Both promargin and retromargin of Himalmartensus chelicerae have 5–8 teeth and the female epigynum is modified with long and looping copulatory ducts. The spinnerets of all three new species are described and tracheal tubes of H. martensi are examined. Spinnerets, colulus, chilum and tracheal tubes of Himalmartensus are compared to similar genera, including amaurobiids, agelenids, and cybaeids. Himalmartensus is defined as a member of the family Amaurobiidae because of its similarity to the amaurobiids Rubrius and Macrobunus.

This study deals with the comparison of spider diversity and composition in a complex landscape of the Terai Conservation Area (TCA) characterized by alluvial floodplains of tall grassland interspersed with woodland, swamps, and riparian patches. High water table, annual flooding, and annual grassland fire maintain its dynamic complexity. A mosaic of five vegetation types was sampled for spiders from March 2005 to August 2006 by using pitfall traps and other semi-quantitative collection methods along transects. A total of 3666 adult spiders representing 22 families, 60 genera, and 160 species were found. Using the abundance-based estimator, Chao1, the predicted richness for the total area sampled is 173 ± 8.32 (SD) species. This indicates that the inventory was almost complete at the regional scale (92%). With similar proportions of captured species, rarefied richness value showed that species richness was highest in riparian swamp forest. Comparison of different sites revealed that species composition was much more similar within the same vegetation type than among different vegetation types. Assemblage composition differed the most between riparian swamp forest and plantation. Guild structure varied considerably in relation to the structural quality of vegetation.

Microtityus (Microtityus) franckei sp. nov. is described from both male and female specimens from the transition zone of the Tayrona Natural National Park, located in the Caribbean region of Colombia. The new species, which is the first of the genus reported from Colombia, is characterized, among other features, by reductive neobothriotaxy on the pedipalp femur and chela. The new species raises to 25 the number of known species of Microtityus, ten of which are present in continental South America. A revised diagnosis of the genus, a species check-list, and some biogeographic and taxonomic considerations are included.

The species-level diversity of fossil Chelicerata is summarized for each order. 1952 valid species of fossil chelicerates are currently recognized, of which 1593 are arachnids. In order of abundance they are: Araneae (979 fossil species), Actinotrichida (283), Eurypterida (241), Scorpiones (111), Xiphosura (96), Trigonotarbida (71), Pseudoscorpiones (38), Phalangiotarbida (30), Opiliones (25), Ricinulei (15), and Anactinotrichida (11). Other groups are represented by ten fossil species or fewer. Based on published descriptions, spiders thus appear to dominate the fossil arachnid species assemblage, making up a greater proportion of paleodiversity than their Recent diversity would predict. Scorpions are also overrepresented, particularly in the Paleozoic, compared to their modern diversity. By contrast, groups like mites, harvestmen, pseudoscorpions and solifuges are noticeably under-represented as fossils when compared to modern patterns of diversity.

Among the 64 genera of Triaenonychinae Sørensen 1886 (Opiliones, Insidiatores), two are found in more than one continent: Ceratomontia Roewer 1915 and Nuncia Loman 1902, both occurring in South America, the former occurring also in South Africa, the latter in New Zealand. Until now there were 22 valid species of Ceratomontia, diagnosed mainly by the tarsal formula. In the present paper, a cladistic analysis was performed to test the monophyly of Ceratomontia and study its relationship with the South African triaenonychine genera Austromontia Lawrence 1931 and Monomontia Lawrence 1931. A total of 42 morphological characters were coded for 18 terminal taxa, 14 representing the genera Ceratomontia (from South America and South Africa), Austromontia and Monomontia as ingroup, and two species of Triaenonychinae from South America, one from South Africa and one Adaeinae Pocock 1902 from South Africa as outgroups. The analysis using heuristic search algorithms resulted in 12 most parsimonious trees (L  =  95, CI  =  0.52, RI  =  0.66). The consensus hypothesis did not recover a monophyletic Ceratomontia, instead, the South African species constitute a clade with the Austromontia and Monomontia species. The Ceratomontia species from South America form a clade that is sister-group of the clade formed by the South African genera of the ingroup. The result shows that Ceratomontia is involved in a “Gondwanan relationship,” but also includes other genera, suggesting that it is not a monophyletic group.

Tree trunks link the forest floor and higher canopy layers, thus constituting an important habitat element for many arthropod species, including spiders living in the canopy. We sampled spiders moving on tree trunks in the boreal forest using two trap designs referred to as “bottle traps” (BT) and “cup traps” (CT) placed on both trembling aspen (Populus tremuloides Michaux) and white spruce (Picea glauca (Moench) Voss) trees of similar DBH (diameter at breast height). Over an average of 83.5 ± 6.3 days/trap (48 traps), we collected a total 333 spiders, representing 13 families and 33 species. Clubiona canadensis Emerton 1890 (Clubionidae), Callobius bennetti (Blackwall 1846) (Amaurobiidae), Pocadicnemis americana Millidge 1976 (Linyphiidae), and Orodrassus canadensis Platnick & Shadab 1975 (Gnaphosidae) were the most commonly collected species, representing more than 60% of the total catch. Twenty eight species and 285 individuals were collected by BTs compared to 18 species and 48 individuals by CTs. Catches in BTs included 15 unique species, whereas five species were unique in CT catches. BTs are easier to transport and deploy, they catch more spiders per trap, and appear to more efficiently sample spider diversity. Thus we recommend the use of BTs to effectively sample wandering spiders on tree trunks; however, the use of both designs could increase understanding about the role of tree trunks as structural features linking forest canopies to the ground layers below.

Two new scorpion species are described from Colombia: Ananteris arcadioi sp. nov. from Meta Department and Ananteris dorae sp. nov. from Nariño Department. These new species raise to 62 the number of known species of Ananteris, eight of which are found in Colombia. Some comments on the taxonomy of Colombian Ananteris are included and some characters are proposed to define species whereas the usefulness of others is briefly discussed. A map with the known distribution of the different species in Colombia, a table for some characters, and a key for the identification of the Colombian species of the genus are included.

The hunting behavior of juvenile Yllenus arenarius Menge 1868 in their first week after leaving sub-sand nests was studied. The spiders were tested with prey that can effectively escape (Homoptera) and prey that are not capable of efficient escape (Thysanoptera and larvae of Lepidoptera) in order to assess the complexity of young spiders' hunting tactics. Numerous differences were found in the mode of catching the prey, which indicate that the spiders possess a conditional hunting strategy. The strategy is expressed in: direction of approach, speed of approach, distance of attack and other prey-specific behaviors. The results strongly suggest the pre-programmed background of both the observed behaviors and sensitivity towards certain prey characteristics that enabled prey identification.

Only two specimens of spiders have been described from Jurassic strata, so the recovery of some 400 new specimens from rocks of middle Jurassic age from China signals a dramatic increase in information on fossil spiders of this period. Here, new spiders belonging to the superfamily Palpimanoidea sensu Forster & Platnick 1984, from the locality of Daohugou, Inner Mongolia, are described. Patarchaea muralis n. gen., n. sp. is a true archaeid, represented by both an adult male and female. Sinaranea metaxyostraca n. gen., n. sp., represented by an adult male and juveniles, is a palpimanoid similar to Palpimanidae and Huttoniidae, but is not placed in a modern family.

The abundance, species richness, and assemblage structure of arboreal Oonopidae of Afrotropical rainforests and savannahs was investigated. Canopy-dwelling spiders were collected by insecticide knockdown fogging at 11 rainforest and three savannah sites in West, Central, and East Africa. In two lowland rainforests (Luki, DR Congo, and Kakum, Ghana) and two savannahs (Faro, Cameroon, and Mkomazi, Tanzania) Oonopidae were the second most abundant spider family, comprising up to 22% of the arboreal arachnofauna. In total, 51 species and 11 genera of Oonopidae were recorded from the 14 study sites. Kakum was the most species- and genus-rich site, with 11 species and 5 genera recorded. The arboreal oonopid assemblages were almost invariably found to be dominated by the widely-distributed genera Orchestina Simon and Opopaea Simon, in terms of both abundance and species richness. Orchestina in particular can be highly abundant and can comprise more than 90% of arboreal oonopids in rainforests as well as in savannahs. Species accumulation curves and six nonparametric estimators of total species richness (Chao 1, Chao 2, ACE, first- and second-order jackknife, and bootstrap) were calculated for Luki, Kakum, and Faro to evaluate the level of inventory completeness. In Kakum and Faro the species accumulation curve respectively closely approached and reached a stable asymptote. The selected nonparametric estimators were found to lack predictive power when applied to the Faro data set and appeared to behave similarly poorly on the Kakum sample set.

We describe the mating behavior in the spermatheca-lacking theraphosid species Sickius longibulbi Soares & Camargo 1948. The behavior in captivity of nine pairs of S. longibulbi was videotaped and analyzed. The mating of this species presented an uncommon theraphosid pattern. There is little in the way of overt courtship by the male, the primary behavior seen being the male's use of legs I and II to touch the female's first pairs of legs and her chelicerae. Sometimes the male clasped one of the female's first pairs of legs, bringing her close to him. While the female raised her body, the male clasped her fangs and held her tightly with his legs III wrapped around her prosoma. The male seemed to try to knock the female down, pushing her entire body until she lay on her dorsum. In this phase we observed the male biting the female on the sternum or on the leg joints. When the female fell, the male attempted to position himself at an angle of 90° from the female. These movements appear to demand a lot of energy, particularly because the female is not passive during the mating. Our findings suggest that copulating in this position is, for the male, more successful than adopting other positions because it allows his extremely long palpal bulbs to deposit more sperm in the female oviduct where - since she lacks spermathecae - she retains the sperm. We suggest that the further he reaches into the oviduct, the greater the chance that he will fertilize the female's eggs.

Sociality occurs in less than one percent of all arachnids. Prolonged subsocial behavior with amicable mother-offspring-sibling associations that extend for a year has recently been reported in captive amblypygids, Damon diadema Simon 1876 (whip spiders; order Amblypygi, family Phrynichidae; Rayor & Taylor 2006). Many social animals have the ability to discriminate kin from other conspecifics so that benefits of group-living are preferentially directed toward kin, although kin discrimination is rare in social spiders. To aid in quantifying rates of behavior, we developed a behavioral ethogram of social and agonistic interactions in immature D. diadema. We conducted two experiments that demonstrate the ability of immature D. diadema to recognize and behave differentially toward kin. In a series of cross-introduction experiments, immature kin or non-kin were introduced into social groups to determine whether aggression and non-aggressive interaction rates varied based on their relationship to the resident animals. To test the hypothesis that differences in behavior were due to familiarity with the habitat, rather than with kinship with resident animals, individuals were cross-introduced into unfamiliar habitats with kin or non-kin. In these introduction experiments, kinship determined the level of aggression among individuals while habitat familiarity did not have an effect. Using olfactory cues alone in Y-maze choice experiments, 9-month old amblypygids discriminated their mother from an unrelated adult female and spent significantly more time near their mother. We discuss our results in relation to other examples of kin discrimination in insects and arachnids, and potential benefits to amblypygids at different ages.

Batesian ant mimics – such as salticids belonging to the genus Myrmarachne – resemble their models to deceive potential predators, sometimes including the ants themselves. Myrmarachne species in addition to being striking visual mimics of ants also wave their first pair of legs in the air, much like the antennal movement of ants. Whether this leg movement is part of Myrmarachne species' mimicry is debated. In this study the leg I movement of four Myrmarachne species was investigated, with particular attention given to the frequency and amplitude of the leg waving. Correlations between the leg waving and other behaviors of Myrmarachne species were also looked at. There were interspecific differences in leg I movements, and the leg I waving also depended on other behaviors such as “bobbing” the opisthosoma. Thus the leg I movement of Myrmarachne species is behavioral mimicry of the antennal movement of ants, in other words increasing the spiders' resemblance to the ants to avoid predation. This “antennal illusion” displays characteristics of a plastic trait which has evolved under selection pressure.

Stereotyped behaviors have been routinely used as characters for phylogeny inference, but the same cannot be said of the plastic aspects of performance, which routinely are taken as a result of ecological processes. In this paper we examine the evolution of one of these plastic behavioral phenotypes, thus fostering a bridge between ecological and evolutionary processes. Foraging behavior in spiders is context dependent in many aspects, since it varies with prey type and size, spider nutritional and developmental state, previous experience and, in webweavers, is dependent on the structure of the web. Reeling is a predatory tactic typical of cobweb weavers (Theridiidae), in which the spider moves the prey toward her by pulling the capture thread (gumfoot) to which it is adhered. Predatory reeling is dependent on the gumfoot for its expression, and has not been previously reported in orbweavers. In order to investigate the evolution of this web dependent behavior, we built artificial, pseudogumfoot lines in orbwebs and registered parameters of the predatory tactics in this modified web. Aspects of the predatory tactics of 240 individuals (12 species in 4 families) were measured, and the resulting data were optimized on the phylogeny of Orbiculariae. All species perform predatory reeling with the pseudogumfoot lines. Thus, predatory reeling is homologous for the whole Orbiculariae group. In nature, holes made by insects in ecribellate orbs produce pseudogumfoot lines (similar to our experimentally modified webs), and thus reeling occurred naturally in ecribellates. Nevertheless, outside lab conditions, predatory reeling does not occur among cribellate orbweavers, so that this behavior could not have been selected for in the cribellate ancester of orbweavers. Cribellate spiders are flexible enough as to present novel and adaptive predatory responses (reeling) even when exposed for the first time to conditions outside their usual environment. Thus, the evolution of reeling suggests an alternative mechanism for the production of evolutionary novelties; that is, the exploration of unusual ecological conditions and of the regular effects these abnormal conditions have on phenotype expression.

In this paper, Trechona venosa rufa Vellard 1924 is elevated to species rank, a neotype is designated, the male is described for the first time, and the female is redescribed. Trechona rufa seems to be restricted to the Atlantic Forest of São Paulo state, southeastern Brazil, covering an area along the coast and going up to the southern slope of the Mantiqueira mountain chain. The composition and distribution of the genus Trechona is changed. As a result, only three valid species remain in Trechona, all inhabiting the Atlantic Forest of Brazil. The other species formerly included in Trechona are considered below: T. lycosiformis (C.L. Koch 1842)  =  Avicularia lycosiformis comb. nov., Theraphosidae incertae sedis; T. sericata (Karsch 1879)  =  Linothele sericata (Karsch 1879), Dipluridae incertae sedis; T. adspersa Bertkau 1880  =  Nemesiidae incertae sedis; T. rogenhoferi (Ausserer 1871)  =  nomen dubium.

Intensively cultivated arable land and semi-desert are two dominant habitat types in the arid agroecosystem in the northwest Negev Desert (Israel). The present study compares activity-densities and species richness of spiders in these distinctive habitat types. Sixteen wheat fields and twelve locations in the semi-desert were sampled during the winter growing season of wheat. Semi-desert habitats had more spider species and higher spider activity-densities than irrigated wheat fields. The majority of spider families, namely Gnaphosidae, Thomisidae, Salticidae, Zodariidae, Philodromidae, Dysderidae, and Clubionidae had significantly higher activity-densities in the semi-desert compared to wheat. Only two families, the Linyphiidae that strongly dominated the arable spider community and Corinnidae had higher activity-densities in wheat than in semi-desert. Out of a total of 94 spider species, fourteen had significantly higher activity-densities in semi-desert than in wheat fields and eight species had significantly higher activity-densities in wheat fields than in semi-desert. Spider families and species that dominated the semi-desert communities also occurred in the wheat fields but at lower activity-densities. In conclusion, the semi-desert is a potential source of spider species and families that may immigrate into arable fields during winter. In particular, active hunting spiders may be sustained in crops through immigration from nearby semi-desert habitats.

Several studies have reported that plant structural components can exert strong influences on the density and distribution of spiders. However, little is known about which plant traits mediate specific associations between spiders and plants. In southeastern Brazil, the lynx spider Peucetia flava Keyserling 1877 (Oxyopidae) is commonly found on the plant Rhyncanthera dichotoma (Melastomataceae), a shrub that bears glandular trichomes. In this study we investigated if Peucetia occurs strictly on Rhyncanthera and what plant parameters influence the spiders' distribution. In addition, we recorded the vertical distribution of spiders of different ages in the plant canopy. Throughout the year Peucetia was observed only on the glandular plant Rhyncanthera, indicating that this association is specific and predictable. Statistical analysis showed no difference in the number of spiders between plants of Rhyncanthera with and without flowers, suggesting that this specific association is mediated by the presence of glandular trichomes, and not by reproductive structures. The distribution of Peucetia over the year was related to the number of arthropods on plants, as well as the number of leaves and height of the host plants, indicating that Peucetia probably choose sites of high food availability. Adults and subadults occurred on higher places on the crown than young and juveniles.

The laterally positioned eyes of stylocellid mite harvestmen are simple ocelli composed of a uniconvex cuticular lens, a lentigen layer, a retina, and a layer of pigment cells. Basal laminae separate the lentigen layer (preretinal membrane) and the pigment layer (postretinal membrane) from the retina. The retina is composed of retinular cells and glial cells. The optic nerve comprises mostly afferent axons formed by the retinular cells, which are accompanied by glial cells. Likely there are also few efferent axons. The retinular cells are characterized by their peculiar nuclei, numerous granules and indications of high membrane turnover. A prominent central region of the eye shows numerous, but poorly ordered interdigitations of long microvilli-like processes presenting a poorly developed closed rhabdom. A smaller region with microvilli forming a rather disordered, open rhabdom is located opposite to the lens. The retina is proximally and laterally surrounded by pigment cells containing, in addition to the usual dense granules, some crystalline inclusions, which may act as a tapetum. Hence, the retina seems to be composed of a proximal part and a distal part with two differently organized simple rhabdoms. The eyes of Stylocellus thus show basically the same organization as the median (primary) eyes of other Opiliones and are likely laterally displaced median (primary) eyes. The occurrence of these primary eyes in Stylocellidae (and Pettalidae) strengthens the idea that the presence of median eyes is thus a plesiomorphic character of these cyphophthalmid harvestmen.

Since the early 1990s managed realignment, where formerly reclaimed land is re-exposed to tidal inundation through breaching of coastal embankments, has been increasingly used throughout Northern Europe as a cost effective and sustainable response to biodiversity loss and flood management. This study aimed to evaluate the success of managed realignment schemes that resulted in salt-marsh development for the restoration of spider assemblages. Restoration of salt-marsh fauna was studied by comparing ground-active spiders between recently inundated land (3–14 years old) and pair-matched, adjacent natural salt marshes. Natural reference salt marshes were characterized by a relatively low species richness, the dominance of late-successional stage species such as Pirata piraticus (Clerck 1757), and the presence of species preferring a closed vegetation canopy like Arctosa fulvolineata (Lucas 1846) and Pardosa nigriceps (Thorell 1856). Restored habitats were characterized by greater species richness than in reference habitat and by the presence of halophilic species (Enoplognatha mordax (Thorell 1875) and Erigone longipalpis (Sundevall 1830)) and abundance of Pardosa purbeckensis (Westring 1861). These preliminary results argue for maintaining a maximum of successional stages in salt marshes, as they increase the diversity of halophilic spiders.

Plantations and secondary forests are becoming dominant components of many tropical forest landscapes. Yet we have an insufficient understanding of the value of these habitats for biodiversity conservation, and almost none for most arthropods in species-rich tropical forests. We sampled epigeic arachnids (Amblypygi, Araneae, Opiliones, Scorpiones, and Uropygi) in primary, secondary (14–19 years), and Eucalyptus plantation (4–5 years) forests in the Jari region of northeastern Brazilian Amazonia. We sampled five independent sites in each forest type between January and June 2005, collecting a total of 4824 individuals (3177 adults, 112 species), including 1864 adults (75 species) in Eucalyptus, 776 (60) in secondary forest, and 536 (72) in primary forest. We compared species richness, species-abundance distributions, and community structure, between the three forest types and identified the species that were characteristic of each forest type. Rarefaction analyses showed that undisturbed primary forest harbored significantly more species and a similar overall abundance as second-growth forest; while levels of species richness were similar between secondary forest and Eucalyptus. The species composition and abundance structure of arachnid assemblages was distinct in all three forest types. Considering all species sampled, 19% were only sampled in primary forest, 4% in secondary forest, and 19% in Eucalyptus. Most species sampled in plantation forests are known to be wide-ranging habitat generalists. Our data indicate that regenerating forests are not biological deserts (57% and 56% of species sampled in primary forest were also captured in secondary and plantation forests respectively) and can, therefore, help mitigate some of the negative effects of deforestation for epigeic arachnids. However, these replacement habitats do not provide a substitute for primary forest and may fail to conserve many of those species most at risk from extinction.

We describe Kochiana new genus to accommodate a small Brazilian theraphosine species described originally as Mygale brunnipes by Koch (1842), resulting in Kochiana brunnipes new combination. Recently, specimens were rediscovered in northeastern Brazilian Atlantic rainforest. A preliminary cladistic analysis using equal weights parsimony and implied weights, was carried out to examine its phylogenetic placement. Kochiana new genus was monophyletic in all trees regardless of weighting scheme or concavity used. There is preliminary evidence for Kochiana new genus monophyly and weak evidence for its placement as sister group of Plesiopelma. Kochiana new genus can be characterized by the presence of a hornshaped spermatheca in females and males with a palpal bulb having prolateral accessory keels and a well developed medial crest on the embolus apex.

The colonization of species on remote islands may result in phenotypic diversification and ultimately speciation. On the Galápagos Archipelago, seven very closely related morpho-species of the wolf spiders genus Hogna are distinguishable based on small somatic and genital differences. Based on habitat preference, these species can broadly be categorized into (i) three “high elevation species” occurring on the volcanic highlands, (ii) three “coastal dry” species occurring in dune habitats along the coast, and (iii) one generalist species which is chiefly found in wet coastal habitats such as salt marshes but also in wet habitats at higher altitudes. To determine the degree of reproductive isolation among these morpho-species, we investigated gene flow among populations and species based on nine allozyme loci. Genetic analysis by means of genetic distance estimates and cluster agglomerative analyses confirmed the status of the defined morpho-species. Allele frequencies were highly similar among populations within a species but differed profoundly among species. Genetic differentiation within the generalist species was generally very low. There were no constant differences between high elevation and coastal populations for this species. Neutral genetic divergence between species appeared to correspond more to geographic distribution rather than to a clear separation of the two different ecological groups within an island. This suggests that a parallel parapatric divergence between high elevation and coastal dry species may have taken place on the oldest islands of San Cristobal and Santa Cruz.

Orbiculariae consists of two major clades: the cribellate Deinopoidea and the much more diverse ecribellate Araneoidea. It has been hypothesized that the higher diversity of Araneoidea is a consequence of the superiority of the viscid orb web. However, this explanation seems incomplete; for example, cribellate silk may perform better than viscid silk in some contexts. Here, we consider the hypothesis that the diversification of Araneoidea was facilitated by changes in microhabitat occupation behavior due to the cheaper viscid orb web. In the present work we investigate the idea that the reduction in site tenacity caused by the emergence of the viscid orb web has led to an increase in the exploration of different resources and to a greater diversification of the Araneoidea through the evolutionary time. To test this idea, we evaluated the response of one cribellate orb web spider (Zosis geniculata Olivier 1789, Uloboridae) and one ecribellate orb web spider (Metazygia rogenhoferi Keyserling 1878, Araneidae) to abrupt prey absence. The changes in site tenacity and the day-to-day investment in web silk were evaluated. Spiders with three-dimensional webs tend to exhibit greater site tenacity than spiders making orb webs. Zosis geniculata and M. rogenhoferi show similar site tenacity when prey is ample. When prey is unavailable, the tenacity of the cribellate species increases while the tenacity of the ecribellate remains unchanged, and the silk investment of both species decreases. However, this decrease in silk investment is more extensive in Z. geniculata. These results coincide with the idea that a less costly ecribellate orb web leads to a lower tenacity and suggest that more frequent microhabitat abandonment in a context of insect radiation (Neoptera) leads to more diverse and opportunistic exploration of microhabitats that, in the long term, may be one explanation for the greater Araneoidea diversification.

Ten theraphosid spiders of the genera Citharognathus Pocock 1895, Haplopelma Simon 1892, Chilobrachys Karsch 1891, Yamia Kishida 1920 and Selenocosmia Ausserer 1871 from China are described, including four new species, namely Selenocosmia xinping sp. nov., S. jiafu sp. nov., S. xinhuaensis sp. nov., and Chilobrachys liboensis sp. nov. Plesiophrictus guangxiensis is transferred to the genus Chilobrachys. Additionally, the species Chilobrachys jingzhao Zhu, Song & Li, 2001 is newly synonymized with Chilobrachys guangxiensis (Yin & Tan 2000).

Spider species respond differently to variations in habitat structure; thus, differences in habitat structure may be responsible for variations in species composition of assemblages. However, little information exists on patterns of variation in spider species composition in tropical rainforests. We collected spiders and measured five different microhabitat characteristics in 20 sampling plots distributed among secondary and primary forest patches in an Atlantic rainforest, Brazil. Using multivariate analysis (non-metric multidimensional scaling - NMS), we checked for the existence of non-random patterns in the species composition of aerial (AG) and ground (GG) macroguilds, respectively. We also explored the relationships of those patterns with gradients in microhabitat characteristics and the influence of forest type (primary or secondary forest). We detected non-random patterns in spider species composition unrelated to microhabitat characteristics but differing between primary and secondary forest plots for both macroguilds. We discuss possible implications for studies of spider species composition and spider conservation in tropical forests.

Pholcidae is the most diverse family among haplogyne spiders but only 15 species have been analyzed cytogenetically. These studies revealed that the diploid number varies from 2n  =  15 to 2n  =  32, that there are three types of sex chromosome systems in males (X, X₁X₂ and X₁X₂Y), and that the chromosomes are predominantly biarmed. Within the genus Mesabolivar, only Mesabolivar luteus (Keyserling 1891) has been karyotyped, and it showed 2n  =  15  =  14 X, with all chromosomes being metacentric. In the present work, we characterize the mitotic and meiotic chromosomes of Mesabolivar brasiliensis (Moenkhaus 1898) and Mesabolivar cyaneotaeniatus (Keyserling 1891). Male mitotic metaphases of the two species showed the diploid number 2n  =  17  =  16 X; oogonial cells of M. brasiliensis showed 2n  =  18  =  16 XX. In both species, the chromosomes were exclusively biarmed, and the X chromosome was the largest element of the karyotype. Diplotene spermatocytes of the two species exhibited 8II X and the occurrence of only one terminal or interstitial chiasma per bivalent. In M. cyaneotaeniaus, metaphases II with n  =  9  =  8 X and n  =  8 were found, indicating the regular segregation of all chromosomes during meiosis I. Mitotic metaphases of M. brasiliensis stained with CMA₃/DA/DAPI revealed GC-rich chromatin in the terminal region of almost all autosomes, especially in pair 2. An earlier revision of the New World pholcids grouped M. brasiliensis and M. cyaneotaeniatus in a “southern group” and placed M. luteus in a “miscellaneous group.” A molecular study showed a closer relationship between M. brasiliensis and M. cyaneotaeniatus than between M. luteus and either of these two species. The 2n  =  17 found in M. brasiliensis and M. cyaneotaeniatus corroborates this hypothesis, given that M. luteus has a diploid number of 2n  =  15.

Making use of the recent publication of a catalogue of spider species from Europe and the Mediterranean Basin, we built a computer database which indexes all specific and subspecific taxa reported from countries or islands in Platnick's world catalogue as well as in regional or national catalogues. We used this database to analyze the distribution of conservation values at the West Palearctic scale. Three indices of conservation value were calculated and compared between mainland and island territories: species richness, number of endemic species, and I_c, a “Conservation Value Index.” Species richness increases with the size of the area being considered, either in islands or in mainland countries, and is highest in Southern Europe. The number of endemics also increases with area, but only for mainland countries, suggesting that different factors determine endemism on islands and in mainland areas. The conservation index shows that several island territories are of a high conservation interest: the Mediterranean and Atlantic islands clearly exhibit the highest conservation value and some islands (mainly Canary and Balearic islands) can be considered hotspots of biodiversity for the West Palearctic area; other hotspots are some small Mediterranean islands.

Tityus stigmurus (Thorell 1876) is one of the most medically important scorpion species in Brazil, but many basic aspects of its life history are unknown. Here the pattern of female reproductive investment was examined, along with development of the 1^st and 2^nd instars and the relationship between 2nd instar mass and molting to the 3^rd instar. Relative to other buthid scorpions, T. stigmurus has a smaller litter (average 10 young) and a shorter 1^st-instar period (average 4 days) and 2^nd-instar period (average 68 days). Neither litter size nor offspring mass showed a relationship to female size. A significant positive correlation was observed between total litter mass and litter size. The minimum mass required for successful molting to the 3^rd instar was 34.0 mg. Overall, female reproductive resources in T. stigmurus appear to be applied to the production of more but not heavier offspring.

Cryptocellus platnicki sp. nov. is described on the basis of specimens of both sexes from two localities in northwestern Colombia. The new species, which is most similar to C. glenoides Cooke & Shadab 1973, brings to 64 the known species of living ricinuleids, and becomes the sixth known from Colombia.

To date, the genus Neostothis Vellard is known only from its type species Neostothis gigas Vellard 1925, described on the basis of a single male and some females from Reserva Biológica do Alto da Serra de Paranapiacaba, Santo André, São Paulo, Brazil. The type specimens, which should be deposited in the collection of the Instituto Butantan are lost. Specimens matching the description of N. gigas, collected in the type locality, allowed us to designate a neotype and provide more information on the genus and species.

Rhopalurus rochai (Borelli 1910) is a very common scorpion species found in the semiarid areas of Pernambuco State, Brazil. This work describes the life history traits of 1^st instar R. rochai such as litter size, development time, dispersal, and survivorship. The development of 2^nd instar juveniles under different feeding regimens was also investigated to determine the effect of food and body mass on intermolt period and number of ecdyses. Field-collected females displaying an enlarged mesosoma were observed daily in the laboratory to obtain newborns that were used to assess events in the 1^st instar. Females gave birth on average to 35.8 young (range  =  23–55). The duration of the 1^st instar (from eclosion to ecdysis) ranged from 7 to 10 days (n  =  179). Dispersal started as early as one day following ecdysis and lasted up to 9 days post-molt. All starved juveniles died between days 11 and 30 of the 2^nd instar. Increasing food ingestion did not enhance the probability of molting, but decreased risk of mortality and increased the time to the second molt. The relationship between the weight changes during feeding experiments suggests that the threshold weight for molt is 34.3 mg. Together these results suggest that developmental periods for R. rochai are slightly greater than those recorded for other buthid genera. These results indicate that there may be inherent physiological costs associated with rapidly increasing mass that may strongly impact foraging strategy.

Grammostola schulzei (Schmidt 1994) comprises a medium-bodied tarantula. Recently the species was found in Sierra de la Ventana, Buenos Aires, Argentina, where it lives in burrows always made under stones in rocky hills. Our objective was to offer a detailed description of courtship and mating, heretofore unknown, and to determine, under laboratory conditions, where copulation takes place: in the open field as proposed for all species of Grammostola, or at the entrance of the burrow. We carried out two series of experiments, completing 40 trials (20 in open arenas and 20 in burrowing arenas). All males initiated sexual behavior after contact with female silk. Courtship involved palpation, palpal drumming, body vibrations, and leg tapping. Palpation and palpal drumming appeared to operate in different ways. Females displayed typical behavior of a burrowing tarantula, making rapid bouts of tapping vigorously with the first pair of legs and palps. The mating position observed was typical of mygalomorphs, in which the female raises her body up and opens her fangs, the male uses the tibial apophyses to clasp the female's fangs, and finally begins a series of attempts at palpal insertion. The smooth slapping during clasping may serve to keep the female passive and relaxed. The dorsal flexion observed during mating and the number of successful matings in open arenas suggests that copulation would take place outside the burrow. We observed sexual cannibalism during the interactions but in these cases, we registered no previous courtships by the males.