This study explores the web-building behavior of Gradungulidae for the first time, using the Otway odd-clawed spider Progradungula otwayensisMilledge, 1997. The web consists of a signal line leading to a retreat, an upper scaffold and a cribellate catching ladder connected to the substrate. The construction sequence and final structure of the catching ladder are highly stereotyped, especially in the initial segments of the cribellate capture thread. Two vertical rail lines—made of thin cribellate silk that is not combed with the calamistrum—are connected by looping segments of combed, much thicker cribellate capture threads. Small juveniles make a relatively larger non-sticky supporting scaffold with some cribellate silk on it. Microscopic analysis of the silk revealed that the cribellate bands have a pair of axial lines and a pair of reserve warps; the cribellate fibrils have nodules. The non-sticky structural lines are made of straight or coiling lines, changing gradually from straight to coiling; each of these structural lines is composed of tightly appressed fibrils, probably associated with the occurrence of multiple ampullate gland spigots. During combing behavior both legs IV are used synchronously. The same combing behavior is performed by the Tasmanian cave spider Hickmania troglodytes (Higgins & Petterd, 1883). We conclude that both type I and type II combing behaviors are monophyletic, although it is unclear which one is ancestral. Given the phylogenetic position of ProgradungulaForster & Gray, 1979, we suggest that the ability to measure with precision and produce repetitive, stereotyped silk structures made of specific silk types may have arisen close to the ancestor of araneomorph spiders.

Despite recent interest, there still is relatively little known about the ecology and physiology of diel and circadian rhythms in spiders. However, previous work on spiders suggests that there is a striking amount of variation in circadian period both among, and within, species, when compared to model organisms. Whereas previous studies of behavioral rhythms in spiders focused on females, here we describe the diel and circadian patterns of locomotor activity in male Parasteatoda tepidariorum (C. L. Koch, 1841) (Theridiidae). We found that the males showed mostly nocturnal activity under a light:dark cycle, with activity peaking very early after lights off and steadily declining to near zero just prior to lights on. Under constant darkness most individuals showed significant circadian rhythmicity with a mean free-running period of about 21.2 h. Though not the shortest average free-running period described for spiders, being so out of resonance with the 24 h solar day strains conventional circadian rhythm theory. Our data also suggest that the phase angle of entrainment for locomotor activity is in the mid-to-late photophase, but that activity may be masked by light. Of particular note is that both the diel and circadian activity patterns reported here for male P. tepidariorum are similar to those reported elsewhere for females of the species. This study deepens our understanding of the nature and variation in circadian rhythm in spiders and builds a case for further developing spiders as a model system for research integrating the fields of chronobiology and ecology.

The spider genus Histopona Thorell, 1869 (Araneae: Agelenidae) includes several species that exhibit a preference for subterranean conditions, being occasionally or exclusively found in caves, crevices and similar habitats. Within the genus, the species displaying the highest level of subterranean adaptation is possibly H. palaeolithica (Brignoli, 1971). This species was described based on a female collected in 1967 in a cave on the Western Ligurian shore (Italy), but had never been recorded thereafter. Our recent biospeleological surveys at the type locality failed to recover the species, possibly because the cave has been impacted by the expansion works of a large quarry. However, we found a new population in a cave opening a few hundred meters away from the type locality. As a result of this finding, we provide the first description of the male, as well as a re-description of the female. We also describe a new species of Histopona based on a female specimen that was collected in a cave in Montenegro, and was previously attributed to H. palaeolithica. In light of the rarity of these specialized stenoendemic species, we provide general information on their ecology and conservation status, as well as information useful for assessing their extinction risk based on International Union for Conservation of Nature (IUCN) guidelines.

Accurate estimation of invertebrate biomass is essential for studies of ecosystem structure and function. To estimate seasonal changes in spider biomass on canopies of two coniferous and three broadleaf tree species in plantation and native forests of subtropical Taiwan, 6,554 spiders were collected from February to August 2015. A part of the collection (n = 887) was weighed and measured to develop appropriate body size-mass equations for subtropical montane forest systems. By comparing different equations, we demonstrate that use of shape-specific equations and incorporation of body width measurements provide the most accurate biomass estimates. Generalized whole-fauna equations produced accurate estimates for the entire pooled sample but caused relatively higher biases than shape-specific equations when applied to spider assemblage subgroups. Applying coefficients derived from the best equations, we describe the seasonal variation in spider biomass on five dominant tree species. Compared to broadleaf trees, Taiwan cedar and Japanese cedar supported higher spider biomass and abundance. Spider biomass on the two conifers declined in early spring, then increased over time, and reached its highest in August. In contrast, spider biomass on caudate-leaved chinkapin and Mori oak formed bell-shaped curves with a high peak in late spring. Spider biomass on deciduous Formosan alder remained at a low level from February to June and increased in August. Moreover, phenological patterns of spider biomass differed from those of abundance on some tree species. We expect that regression parameters from our study are appropriate for biomass estimation of spider assemblage in subtropical montane forest systems.

Mygalomorphs are a well-known spider group; however, astonishingly little is known about their internal anatomy. As part of a comparative survey on the circulatory system in spiders, we conducted an examination of the hemolymph vascular system (HVS) and parts of the hemolymph lacunar system (HLS) in five mygalomorph spider species. Circulatory system features were investigated using micro-computer-tomography in combination with resin injection methods and serial sectioning. Data were visualized using a 3D-reconstruction software. The HVS consists of a tubular heart, which is situated along the dorsal midline of the opisthosoma. Anteriorly, the heart gives rise to the anterior aorta. A posterior aorta system was not found. Three pairs of cardiac arteries originate laterally from the heart and the branching pattern of these arteries is visualized and described here for the first time. The anterior aorta runs through the pedicel into the prosoma where it branches to supply the muscles and particularly the central nervous system. The data on mygalomorphs are discussed in comparison to the HVS in other Araneae.

Sexual dimorphism between females and males can sometimes be related to particular mating behaviors. In pseudoscorpions, very little is known about the relationship between sexual size dimorphism (SSD) and reproductive behavior. This paper describes sexual dimorphism and the mating behavior patterns of Lustrochernes argentinus (Thorell, 1877), a Neotropical species of Cheliferoidea. We measured different body structures and appendages of 14 individuals of each sex, with the values compared with a T-test. We also analyzed the sexual behavior repertoire occurring during mating between nine couples. We found SSD for several structures: the fixed and movable finger width, and the angle between IV coxae are larger in females, in contrast with the gap between fingers which is bigger in males. The analysis of sexual behavior patterns in this species showed that the reproductive behavioral repertoire is structured in three phases: Phase I (examination), Phase II (spermatophore deposition) and Phase III (sperm transfer) with a mean duration of 2.2 min, 5 min, and 7.5 min, respectively. Some structures that showed SSD, and also the composition and duration of different behavioral phases, are different from those of other species of the family Chernetidae. We discuss the results based on current knowledge in pseudoscorpion biology with prospects of further studies studying sexual selection.

A new genus and species in the South American sun-spider family Mummuciidae, Curanahuel aconcagua gen. nov., sp. nov., is herein described from Argentina. The new genus is known from two localities in the provinces of Mendoza and San Juan, both located within the Cuyan High Andean biogeographic province. Among other features, this genus can be readily distinguished from other mummuciid genera by the very distinctive ctenidia on the third post-genital sternite, which are exceptionally thick in the male and also notably thick in the female.

Eukoenenia igrejinha sp. nov. is described on the basis of one male and one female from the cave Gruta da Igrejinha, state of Minas Gerais, southeastern Brazil. The new species exhibits morphological features unique among the South American species of Eukoenenia described to date, such as a single pair of paramedian thickened setae flanked by one slender seta on each side of opisthosomal sternites IV–VI and 9 pairs of setae on the first genital lobe of the female. Additionally, we provide the coxal formulae of the South American species E. maquinensis, E. spelunca, E. improvisa and E. janetscheki.

Harvestmen genera with transcontinental distributions are rare but represent very interesting models for evolutionary and biogeographical studies. However, before attempting to understand such distributions, it is crucial to have a good taxonomic foundation of the focal taxa. One of the most disjunct harvestmen genera is NunciaLoman, 1902 (Triaenonychidae), which has been recorded from New Zealand and South America, but the alpha taxonomy is in need of improvement, mainly with respect to the detailed characterization of male genitalic morphology. The taxonomic and systematic revision of Nuncia remains an important and intriguing issue, and the redescription of Nuncia obesa (Simon, 1899) is a necessary starting point for the taxonomic revision of the genus. Herein we redescribe and illustrate N. obesa based on the reexamination of the syntypes of Nuncia sperataLoman, 1902 (type species of Nuncia) and the holotype of Triaenonyx obesusSimon, 1899 (senior synonym of Nuncia sperata). We also confirm the synonymy of both species.

A series of spider drawings and accompanying notes by the naturalist John Abbot (1751–c.1840) served as the basis of many new taxa described by Charles A. Walckenaer. Since the late nineteenth century, researchers have wrongly associated these drawings with Abbot's watercolors of Georgia spiders (and some Opiliones) held at The Natural History Museum, London. In reality, the drawings and notes consulted by Walckenaer are deposited at the Muséum national d'Histoire naturelle in Paris. Six letters preserved with these drawings, dated 1802–1821, corroborate their provenance as published by Walckenaer. This mistaken identity stems from Abbot's practice of duplicating his artwork and written observations. It has yet to be determined how the differences between these collections of drawings will impact species synonymies as they relate to Walckenaer's taxa. One example involves the original concept of Sphasus vittatusWalckenaer, 1837.

Agricultural management should aim at high densities of beneficial organisms such as spiders. Here, we asked whether spiders in vineyards can be promoted either by using novel disease resistant grape varieties that allow for a reduced number of fungicide applications, or by minimal pruning which enhances the structural complexity of the grapevine canopy. We compared spider communities in vineyards planted with fungus-resistant varieties (PIWIs) to vineyards with traditional grapevine varieties, and minimally pruned vineyards to vertical shoot positioned vineyards. Densities of Theridiidae were more than doubled in fungus-resistant grape varieties, but the remaining families were not significantly affected. Minimal pruning enhanced Philodromidae and Dictynidae but reduced Salticidae. However, neither pruning method, nor the reduced fungicide use in PIWI vineyards, had significant effects on overall spider abundance or species richness. Hence, effects of vineyard management were family-specific and possible consequences for pest regulation will thus depend on the pest control potential of the involved families.

Absence of light is a fundamental characteristic of subterranean ecosystems; thus, productivity must be supported indirectly by influx of detritus from effulgent environments. I examined how this influx impacts the carrying capacity of a cave predator: the whip spider Phrynus longipes (Pocock, 1894). Although solitary, territorial and cannibalistic, this species occurs at extremely high densities in caves. To test the hypothesis that this is an effect of nutrient flow and not cave structure, I examined whether guano deposition at cave entrances predicted estimated population sizes of whip spiders. I found a strong correlation, suggesting that whip spider carrying capacities are at least partly determined by nutrient influx to the cave ecosystem. Larger guano deposits support a larger community of arthropod detritivores, which act as prey to this top predator in a bottom-up effect. This highlights the importance of considering surface environmental and population health along with commercial guano harvesting when studying and conserving caves and the species therein.

Sensory ecology studies show that reception and utilization of information from the environment is a crucial life process. Scorpions possess a weapon that can be used against predators, but it remains unknown whether scorpions' decision to use it is influenced by chemical cues from predators. We investigated the influence of predators' odors on stinging behavior of Hadrurus arizonensis (Ewing, 1928) by stimulating them to sting under two conditions: in the presence of an odor from a potential rodent predator (Rattus norvegicus) and in the absence of such an odor. It took fewer probes to elicit a response when predator scent was present, and it resulted in more wet stings than the non-scented treatments. Finally, the smaller scorpions were more reactive than the larger ones. The variances in stinging behavior suggest that the detection of predator odors by H. arizonensis elevates its response in potentially threatening circumstances.

In many invertebrates, the monoamine octopamine (OA) acts as a hormone and neurotransmitter, regulating “fight-or-flight” behavior and aggression. Though well-studied in some taxa (e.g., insects and crustaceans), the role of OA in arachnids is little understood, and information on any hormones within scorpions is lacking. Given its effects in most arthropods, we expected elevated levels of octopamine to increase aggressive antipredator behaviors in scorpions. We experimentally raised octopamine levels in striped bark scorpions (Centruroides vittatus (Say, 1821)) and measured changes in their behavioral responses to simulated predator attack. Elevated octopamine levels increased aggressive behaviors in C. vittatus scorpions, whereas an octopamine antagonist (phentolamine) had no effect on behavior. Overall, this study begins to extend our understanding of behavioral endocrinology to scorpions, finding general similarities with spiders. Future work promises to better elucidate the role of monoamines and other hormones in regulating scorpion behavior and their interactions with predators.

The defenses of harvestmen encompass nipping with spines, releasing of chemicals, fleeing, bobbing, crypsis, and death feigning. Animals are expected to invest more in death feigning in situations in which they are more vulnerable to predation. For prey species attacked by visually-oriented predators, death feigning should be more frequent in daytime than during nighttime. Here, we used the harvestman Mischonyx cuspidatus (Roewer, 1913) (Gonyleptidae) to test whether: (i) individuals perform death feigning during daytime more often than during nighttime; (ii) individual body condition influences the time and frequency of death feigning. We found support for the former prediction, but not for the latter. Our results are in accordance with the hypothesis that among harvestman death feigning would be an advantageous passive defense against visually oriented predators. In this study, for the first time, we demonstrate that harvestmen show differences in death feigning behavior depending on light conditions.