Primary chemosensory afferents within each peg sensillum on scorpion pectines contain a dense plexus of synaptic contacts of unknown importance to informational processing within this simple sensory structure. These connections probably contribute to the processing of chemical signals from the substrate to the encoded pattern of spike activity ascending the pectinal nerves to the CNS. A key finding of earlier studies of this system was the apparent existence of strong and long-lasting inhibitory interactions between one identifiable unit – type “B” cells – and at least two other sensory neurons – identified as “A1” and “A2” – cells within the same sensillum. Because peripheral synaptic interactions are rarely observed between primary sensory neurons, it is important to reject the alternative non-synaptic mechanism to account for the unusual spike waveform of inhibitory B units, namely, that it is derived from coincident discharge of the A1 and A2 units it is presumed to inhibit. High resolution waveform analysis of two or more units firing in close temporal proximity (within about 5 ms) showed unequivocally that type B units occur within the post excitatory period when the A units would be refractory to re-excitation. Furthermore, the number of these B/A1 or B/A2 doublets was in line with the number predicted for the observed spontaneous firing frequency of the B, A1, and A2 units in the peg. This analysis corroborates the original conclusion that B unit activity is the electrophysiological signature of an inhibitory processing event, one that strikingly transforms the information encoded and passed from each peg sensillum to the central nervous system.

Our focus was to design harvestmen-specific PCR primers to target both introns and exons of the nuclear protein-coding gene Elongation Factor -1 alpha (EF-1α). We tested this primer set on ten genera representing all primary lineages of Opiliones, with sets of close phylogenetic relatives (i.e., sets of several congeners) included to specifically assess utility at shallow phylogenetic levels. Our research also included the collection of parallel mitochondrial protein-coding DNA sequence datasets for the congeneric sets to compare relative rates of evolution and gene tree congruence for EF-1α versus mitochondrial data. The harvestmen primers resulted in successful amplification for nine of ten tested genera. Exon sequences for these nine genera appear orthologous to previously-reported EF-1α Opiliones sequences, which were generated using RT-PCR methods. Newly-generated exon sequences are interrupted by three separate spliceosomal introns; two introns are restricted to one or two genera, but a third intron is conserved in position across all surveyed genera. Phylogenetic analyses of EF-1α nucleotide data for congeneric sets result in gene trees that are generally congruent with mitochondrial gene trees, with EF-1α phylogenetic signal coming from both intron and exon sites, and resolving apparently recent divergences (e.g., as recent as one million years ago). Overall, the combination of gene orthology, conserved intron position, and gene tree congruence at shallow levels suggest that this gene region will prove generally useful for both phylogeographic and species-level phylogenetic analyses in Opiliones, complementing already-documented utility at higher taxonomic levels.

A great number of spiders build orb-webs and although the overall structure is the result of fixed behavioral patterns, much small-scale inter- and intraspecific variation is nonetheless evident. Thus in order to fully understand the orb-web and web-building behavior in these spiders, we need to study substantial samples of many different species of orb-weavers. However, to date only a few species have been rigorously studied both in the field and in the laboratory. Here, we investigate the ecology, behavior and orb-web of the neotropical spider Eustala illicita (O. Pickard-Cambridge 1889) and suggest it as suitable for further studies based on 1) the ease at which it can be located in abundant numbers in the field, 2) its willingness to build webs in the laboratory, 3) the plasticity of its behavior, and 4) its interesting ecology in the form of interactions with the swollen-thorn acacias and their ant mutualists. Here, we introduce its natural history and then provide a detailed description of orb-webs built in the field and in the laboratory, which we compare to other orb-spiders.

Despite the conceptual appeal of how morphological mimics visually distinguish between conspecifics and their models, scant attention has been given to this topic. Accurate discrimination between ants and conspecific spiders is likely to be under strong selection because approaching an ant may result in the spider's death, while approaching a different sex conspecific may result in copulation. I addressed this question by examining responses of the ant-like jumping spider Myrmarachne bakeri Banks 1930 (Salticidae) toward motionless, odorless lures made from dead conspecifics, ants, or lures using components of non-ant-like salticids, ant-like salticids and ants. I found that chelicerae, legs I and body, but not movement, are important cues used by M. bakeri to distinguish conspecifics from ants, but the relative importance of these cues differs depending on a spider's sex.

A new species, Mesobuthus bolensis from the Province of Xinjiang, in the Western region of China, is described. The new species can be defined by a densely granular carapace; carinae, granulation, and metasomal segment V without any dark pigmentation; carinae of carapace and pedipalp patella dispersively granular. Furthermore, restudy of the characters of Mesobuthus songi Lourenço, Qi & Zhu 2005, described from the southern region of Pulan, Xizang (Tibet), China led us to accommodate this species in the genus Hottentotta Birula, as a new combination Hottentotta songi (Lourenço, Qi & Zhu 2005).

Areomartus ovatus Petrunkevitch 1913, from the Pennsylvanian (Kanawah Formation; Bashkirian?) of Cotton Hill, Fayette County, West Virginia, USA is redescribed. Originally placed in the family Eophrynidae of the extinct arachnid order Trigonotarbida, it lacks unequivocal eophrynid features. Nevertheless, Areomartus Petrunkevitch 1913 was used as the type genus of a now superfluous eophrynid subfamily Areomartinae Petrunkevitch 1955. The present revision suggests that too much emphasis was placed on the primary diagnostic character of Areomartus, hexagonal fields across the carapace, in a rather poorly preserved and incomplete specimen. Areomartus ovatus is thus removed from Eophrynidae and treated as Trigonotarbida incertae sedis. Vratislavia silesica (Römer 1878) from the Pennsylvanian (Langsettian?) of Kłodzko (formally Glatz) in Silesia, Poland is another problematic eophrynid. The holotype is believed lost, and thus interpretations rely on published figures. Opisthosomal morphology suggests that V. silesica actually belongs in a different trigonotarbid family: Anthracosironidae.

Around 1000 obligate cave species have been described from the continental United States. This taxonomically diverse group of species contains both terrestrial obligate cave species (troglobites) and aquatic obligate cave species (stygobites). The greatest diversity of troglobites in the United States occurs on the southern Cumberland Plateau in south-central Tennessee and northeastern Alabama. The troglobitic spider Nesticus barri Gertsch 1984 is known from nearly 60 caves in this area. We studied the mitochondrial phylogeographic structuring of this species, sampling individuals from twelve caves across the species' range. We found that N. barri populations within individual caves are generally not genetically diverse; that N. barri is divided into genetically distinct subpopulations, with mitochondrial cytochrome oxidase I genetic distances between subpopulations ranging from 0.021 to 0.045; and that female-based migration between caves is minimal or nonexistent, even over small geographic scales (< 15 km). This is the first genetic study of a troglobitic taxon from this biodiverse region. Our results contrast with those from previous studies on stygobitic crayfish from this area, which showed high levels of gene flow between caves.

Homologies of the tibial apophyses of Taira with those of other members of the subfamily Amaurobiinae are evaluated. The monophyly of the genus Taira and the phylogenetic relationships of its species are analyzed using parsimony. The genus Taira is supported by two putative synapomorphies: the presence of broad epigynal teeth and the distally originating tegular sclerite apophysis. A diagnosis and description of Taira and a key to its species are provided. Three new species are described from China: Taira qiuae new species (♂♀), T. sichuanensis new species (♂♀), and T. zhui new species (♂♀).

Hentzia alamosa (Salticidae) is described from Big Bend Ranch State Park in Presidio County, Texas, and a closely related species, Hentzia fimbriata (F.O. Pickard-Cambridge 1901) is recorded for the first time from the USA. Both species are also closely related to Hentzia palmarum (Hentz 1832), the type species for the genus. New locality records provided by the Texas A & M University Insect Collection (TAMUIC) for H. palmarum are also included.

The genus Eurocoelotes, established in 2002 with fourteen species from Europe, including two new species, E. halanensis sp. nov. (♀ only) from Mali Halan, Croatia and E. paramicrolepidus sp. nov. (♂ only) from Peloponnisos, Greece, is reviewed. Each species is described with a focus on the male palp and the female epigynum. A key to species is provided. Except for E. deltshevi (Dinitrov 1996) and E. drenskii (Deltshev 1990), specimens of which were not available, we have provided illustrations for the male palp and the female epigynum of all species. In general, the male Eurocoelotes has a short cymbial furrow, a broad conductor dorsal apophysis, a spoon-shaped median apophysis, and a prolaterally originating embolus, but lacks a patellar apophysis. The female Eurocoelotes usually has laterally arising epigynal teeth, a large, anteriorly situated atrium, large copulatory ducts, and short, slightly longitudinally extending spermathecae. Exceptions include: E. falciger (Kulczyński 1897), which has a long cymbial furrow and a proximally originating embolus, E. anoplus (Kulczyński 1897) and E. gasperinii (Simon 1891), which have proximally originating emboli, E. brevispinus (Deltshev & Dimitrov 1996), which has a distinct patellar apophysis, E. microlepidus (de Blauwe 1973) and E. paramicrolepidus, which have a tiny patellar apophysis, and E. xinpingwangi Deltshev 2009, which has no epigynal teeth.

Spiders spin a variety of task-specific silk fibers, each composed of one or more unique proteins synthesized within specialized glands in the spider's abdomen. Tubuliform glands are the source of the large diameter silk fibers used by many species in the construction of egg cases. Unlike other silk glands that synthesize protein throughout a spider's lifetime, the tubuliform glands synthesize silk in association with the maturation of oocytes, culminating in the production of an egg case. In the Western black widow, Lactrodectus hesperus Chamberlin & Ivie (1935), egg case fibers are composed of at least three proteins: tubuliform spidroin 1 (TuSp1), egg case protein-1 (ECP-1), and egg case protein-2 (ECP-2). Here, we present the first study to quantify the pattern of transcription for these three genes in a developmental series of tubuliform glands from L. hesperus. All three transcripts increase in abundance prior to the production of an egg case, but at different time points. After egg case production, silk transcripts are still detectable in the tubuliform glands. Relative abundance of TuSp1 mRNA is several orders of magnitude higher than that of ECP-1 and ECP-2 at almost every stage. The relative abundance of silk transcripts across the reproductive life history of black widows suggests differential regulation of silk gene transcription within tubuliform glands.

The new genus Agnostopelma Pérez-Miles & Weinmann is proposed for the type species A. tota n. sp. and A. gardel n. sp. from Boyacá, Colombia. Agnostopelma build shelters under stones at high elevation. The new genus is unusual in lacking tarsal scopulae on its posterior legs and in having few labial cuspules and short leg tarsi in females.

A new species, Dasylobus nevadensis, is described; it inhabits high areas of the Sierra Nevada, the highest mountain chain in Spanish mainland. The new species is smaller than all other Iberian Dasylobus species and has short, annulated legs, light silver coloration, and is juvenile-like. Together with Roeweritta carpentieri (Roewer 1953), this is an orophilous endemic species from Sierra Nevada.

Ladder-webs are built by several orb-web spider species and can be divided into two main groups based on the microhabitat in which they are built, either in open spaces (aerial) or against tree trunks (arboricolous). In Australian ladder-web spiders, Telaprocera, the elongated webs are a highly plastic behavioral response to building in space-limited conditions against tree trunks, while the aerial ladder-webs of Scoloderus are an adaptation for catching moths. However, the relative importance of moth capture in the construction of elongated webs in arboricolous spiders cannot be determined with existing data. We here present observational and experimental data concerning prey capture in the arboricolous spiders T. maudae Harmer & Framenau 2008 and T. joanae Harmer & Framenau 2008. We found that moths make up only a small fraction (< 4%) of the diet of Telaprocera spiders and that the proportions of major prey orders in webs are representative of available prey. Our experiments indicate that these webs do not function well at retaining moths. However, further data are required before more definite conclusions can be drawn regarding whether these webs are more effective at retaining moths than standard orb-webs.

Since venom is costly to produce and stinging is not obligatory in prey capture for scorpions, the need to optimize use of resources suggests that venom should be reserved for prey that cannot otherwise be overpowered, (i.e., larger and/or more active prey). In accordance with these predictions, sting use by Hadrurus spadix Stahnke 1940 increased with prey size, reaching 100% once prey items were longer than the scorpion's pedipalp patella length, and with prey activity, which we manipulated by varying prey temperature. Surprisingly, the scorpions were slower to capture less active (cooler) prey than those that exhibited higher rates of activity. We suggest this is because prey are located by vibrations in the substrate, with less active prey producing fewer vibrations.

The stygnopsid harvestman Chinquipellobunus madlae (Goodnight and Goodnight 1967) is known from numerous caves in eleven counties in Texas and is a highly adapted troglobiont (Cokendolpher 2004). Adult and juvenile specimens were extracted in methanol, and the major volatile component of their chemical defense secretion was identified as 2-methyl-5-ethylphenol; a minor component was 2, 5-dimethylphenol. Methylethyl phenols and dimethyl phenols have also been identified in other grassatorid Opiliones, but this is the first report of defensive chemistry from a member of the family Stygnopsidae and from a North American troglobiont harvestman.

The presentation of nutritional resources as nuptial gifts before or during the mating process is well known among insects, but has only rarely been documented in spiders. Here, we report on observations and a series of photographs made during field studies in Fortin de las Flores, Veracruz, Mexico, which, although a single anecdotal report, represent a potentially significant finding. A male of the kleptoparasitic spider Argyrodes elevatus Taczanowski 1873 (Araneae, Theridiidae) was observed stealing a prey item from within a communal web of its host, the colonial orb-weaver Metepeira incrassata F.O. Pickard-Cambridge 1903 (Araneae, Araneidae). The male A. elevatus then carried and presented the prey item to a female, waited nearby until she began feeding, and copulated with her as she fed upon it. As far as is known, this is the first report of kleptoparasitic Argyrodes apparently utilizing a prey item stolen from a host spider as a nuptial gift.

Nuptial gifts in spiders are poorly documented. We report on an observation and on photographs of a colonial web in San Vicente de Chucurí, Santander, Colombia, which suggest a likely case of nuptial gift behavior in a male of the kleptoparasitic spider Argyrodes elevatus Taczanowski 1873 (Araneae: Theridiidae). Pictures of a male A. elevatus holding a dead Cyclosa huila Levi 1999 (Araneae: Araneidae) wrapped in silk, in close proximity to a female A. elevatus facing him, document the couple at various moments at dusk and early the following morning. While no copulation is seen, these pictures suggest an attempt by the male to deliver a nuptial gift. Our observations support a recent report of apparent nuptial gift behavior in A. elevatus and raise questions on the foraging behavior of kleptoparasitic spiders in communal webs.

Although well studied, the role of spider webs in attracting prey and the role of web ornaments remain open questions. We carried out a field study to determine whether webs of Nephila clavipes (Linnaeus 1767) attract insects. Nephila builds large orb-webs with debris-decoration that host kleptobiotic Argyrodes spiders. We studied the potential prey of Nephila with sticky traps placed in two similar linear plots. One plot contained 20 Nephila webs, and the other was cleared of Nephila webs. We measured the number and size of the insects caught in the traps. We compared the size of the trapped insects with prey caught by Nephila and gleaned by Argyrodes. In the plot with Nephila webs we collected 314 individuals versus 105 individuals in the plot without Nephila. Species of Diptera and Coleoptera were captured most frequently. Four saprophagous families, Phoridae and Sciaridae (both Diptera), Staphylinidae and Elateridae (both Coleoptera), were more abundant in the plot with Nephila webs. We show for the first time under natural conditions that prey attraction is most efficient for saprophagous insects, suggesting that the debris-decoration in Nephila webs attracts this guild. We also found that the size of some insects captured does not correspond to the range of prey consumed by Nephila, but to that of kleptobiotic Argyrodes spiders. We hypothesize that the debris-decoration may be used by Nephila as a strategy to limit food competition with Argyrodes.

Myrmarachne bakeri Banks 1930 is a polymorphic, generalized ant-mimicking jumping spider. In this study, variation in its polymorphic characters was observed and described. Myrmarachne bakeri varies in color, glossiness and patterns; and differs from other polymorphic ant-like spiders because it becomes polymorphic before adulthood. Morphological changes appear to have no set archetype, and few spiders revert to morphs previously observed. Polymorphism is widespread in Myrmarachne, but to date no species has been shown to exhibit the type of variation found in M. bakeri.

Poeciloneta bellona Chamberlin and Ivie 1943 is removed from synonymy established by Saaristo and Tanasevitch (2000) and re-described using new and existing specimens from the Rocky Mountains. Incestophantes calcaratus (Emerton 1909) is re-described and transfered to Poeciloneta Kulczyński 1894 and a lectotype is designated.

The first blind Australian species of Tetrablemmidae and only the fourth in the world, Tetrablemma alaus, new species, is described from subterranean habitats in northwestern Australia. The total loss of eyes is correlated with its subterranean existence and is complemented by other troglomorphies including slightly elongated appendages and pale coloration.

Nephila spiders are famous for extreme sexual size dimorphism, with females an order of magnitude larger than males. The proximal developmental mechanism for the sexual size dimorphism is extended development in females: they have many more juvenile instars than males. During an experimental rearing of Nephila clavipes (Linnaeus 1767) from two populations, we discovered that females cannot reach sexual maturity on diets that are qualitatively and quantitatively sufficient for male maturation. Here we describe the dietary regimes that produced sexually mature females and the life history implications of these requirements.

We describe a new unusual setule on type IV urticating setae of the theraphosid spider Homoeomma uruguayense (Mello-Leitão 1946). These processes have a filiform stalk and a funnel-like apex that arise from the main axis of the urticating seta. The probable function of these structures in passive and active defense is discussed.