Current Issue

Scorpions are diverse and abundant in tropical and subtropical regions worldwide, especially in arid ecosystems where they play a relevant role as predators. However, few studies have examined diet composition, use of alternative foraging strategies, prey selection, and predator-prey size relationships of scorpions in different microhabitats. This study provides an analysis of the diet of Buthus montanus Lourenço & Vachon, 2004 in an arid area of SE Spain. Prey captured by scorpions were recorded during black-light censuses over the main activity season of B. montanus in the study area. Because scorpions were observed capturing prey on the ground surface, below ground, and in vegetation, prey availability was estimated using complementary methods for shrub- and ground-dwelling prey. Results show that B. montanus is a generalist predator that feeds on a diverse array of prey, although predatory arthropods and tenebrionid larvae comprised the highest proportion of its diet in both number of prey and biomass. Cannibalism was a major component of its diet, accounting for almost 25% of the biomass ingested, especially in large scorpions. The composition of the diet, prey-size variability, and predator-prey size relationship showed size-related differences. These size-related variations in the diet were also linked to habitat use, due to climbing vegetation by smaller scorpions. These results highlight the implications of ontogenetic shifts in the diet of B. montanus related to cannibalism by larger scorpions and climbing vegetation by smaller individuals, causing changes in the type of prey used by individuals of different size and predator-prey size relationships.

Australia is home to an incredible diversity of spiders, but much of their biology remains unstudied. The orb-weaving spiders (family Araneidae) are especially diverse and frequently encountered, yet the ecology of very few species has been explored. The common name “Australian garden orb-weaver” refers to several species, including Hortophora transmarina (Keyserling, 1865), found mostly along Australia's east coast, and Hortophora biapicata (L Koch, 1871), found mostly along Australia's south and south-eastern coasts. These two similar species are large, nocturnal orb-weavers that occupy a wide range of both natural and anthropogenically disturbed habitats. Here, I describe the general morphology, habitat use, diet and foraging behavior, key predators, laboratory rearing, and mating dynamics of these common but understudied spiders. This information was gathered via field observations, laboratory experiments, and literature reviews. These spiders provide a useful system for studying a number of aspects of spider biology, including mating systems, predation, anti-predator defences, and nocturnal behaviors.

Vinegaroons in the high desert grasslands of southeastern Arizona spend much of the year in deep sealed underground cells and dig to the surface when the first summer rains begin in late June or during July. They are active only at night, when they are large apex ambush predators that prey on a variety of small, surface-dwelling animals. Adult and last instar immature vinegaroons were frequently observed, whereas the smaller first three instars were rarely seen. Using mark-capture techniques, the density of individuals in the area was found to be at least 95 individuals/ha to as high as 680 individual/ha. The population profile remained mostly steady over several years with adults and 4^th instar immatures constituting 90% of the observed population. Females were mainly present during the earlier part of the foraging season. In contrast, males were active much longer and until the end of season. The three first instars of vinegaroons spent little time on the surface of the ground partly because they are vulnerable to predators and partly because they require few prey items to accumulate the necessary reserves for molting to the next instar. About 12% of the population had injuries, or signs of previous injuries. Most injuries were to their tail-like flagellum, with a few sensory leg injuries. Short, regrown flagella in field individuals showed their ability to regenerate these lost appendages and laboratory experiments demonstrated that vinegaroons can regenerate lost parts of sensory legs and even their hard, powerful pedipalps.

Orb webs constructed by members of the spider family Uloboridae are characterized by the presence of cribellate thread on frame lines and cribellate thread placed on radii to form zig-zag patterns in a web's perimeter. Both features are added before more typical, fully circular capture spiral production begins. Zig-zags give the impression that a spider is filling in the gaps between a web's outermost spiral and frame line, although they are constructed before capture spiral turns begin. We examine these traits in orb webs of six species (Philoponella vicina (O. Pickard-Cambridge, 1899), Siratoba referens (Muma & Gertsch, 1964), Uloborus glomosus (Walckenaer, 1841), Uloborus trilineatus Keyserling, 1883, Waitkera waitakerensis (Chamberlin, 1946), and Zosis geniculata (Olivier, 1789). In four species, the distance between the outermost capture spiral and frame line was correlated with the length of cribellate thread on a radius. A web's capture area increased as the area encompassed by zig-zags was added to that encompassed by the outermost fully circular cribellate spiral thread and again when cribellate thread on frame lines was included. When constructed in frames of the same size, webs of S. referens and U. glomosus were less symmetrical and contained more capture thread switchbacks per spiral turn and per web area than did horizontal orb webs of Leucauge venusta (Walckenaer, 1841) (family Tetragnathidae). Features in the perimeter of uloborid webs may adapt these small spiders to irregular spaces within vegetation by allowing them to cover larger portions of their webs with sticky lines.

The Paratropididae Simon, 1889 comprises small to medium-sized (6.0–18.5 mm) mygalomorph spiders with 26 species distributed in four genera: Anisaspis Simon, 1892; Anisaspoides F. O. Pickard-Cambridge, 1896; Paratropis Simon, 1889 and Stormtropis Perafán, Galvis & Pérez-Miles, 2019. Paratropidids can be found in tropical and mountain forests, in caves, near rivers, under fallen logs and rocks, leaf litter, moss and ravines. Most species are distributed in South America, mainly in Colombia, Ecuador and Brazil. Despite recent efforts in understanding the taxonomy of the family, paratropidids are still poorly studied. Herein, three new species of Paratropis are described: Paratropis celiae sp. nov. and Paratropis manauara sp. nov., both from Manaus in the state of Amazonas, Brazil; and Paratropis vulcanix sp. nov. from Departamento Tolima-Calda Nevado del Ruiz, Colombia. An updated geographical distribution map for the entire genus is presented and a discussion on the taxonomic problems of the family is provided.

Spiders use information received from trichobothria for capturing prey or escaping predators. However, we have no extensive information on if or how trichobothria might be used in conspecific communication. This study tests the hypothesis that female wolf spiders Schizocosa retrorsa, (Banks, 1911) use their foreleg trichobothria to detect and assess courting males. Prior studies have shown that male S. retrorsa can mate successfully in signaling environments where females cannot detect visual or vibratory signals. Despite this, higher rates of male leg waving still predicted successful mating. In addition to their visual conspicuousness, these rapid leg waves can generate air particle movement that may be detectable by a female's trichobothria. If females use trichobothria to detect and assess male leg waving, then we might predict the following. When female trichobothria are compromised, we expect (i) lower overall mating success and (ii) no relationship between male mating success and leg waving rate. To test these predictions, we ran mating trials in environments unconducive to visual or vibratory signals and compared the mating success and mating predictors of female/ male S. retrorsa pairs across two female treatments groups: (a) foreleg trichobothria unablated and (b) ablated. We found no significant difference between the mating success of the two groups. However, mating success was higher for males that waved their legs at a faster rate in the unablated, but not the ablated treatment groups. Our results indicate that the ablation of female trichobothria interferes with the detection and assessment of male leg waving, supporting a role of trichobothria in receiving air particle movement signals.

The range of trophic niches in spiders varies from very wide, including prey of several insect orders, other arthropods, and even nectar and other plant products, to very narrow, restricted to specific prey types, such as ants. Previous studies showed that the effects of a mixed diet are beneficial to fecundity, survivorship, and growth rate for some species but not others. This study evaluated the impact of a varied diet and monotypic diets of beetles, ants, and termites for Tidarren haemorrhoidale (Bertkau, 1880) a cobweb spider. Adult females were collected in a Eucalyptus plantation, kept in captivity, and divided into four experimental groups; each submitted to one of these diets for 125 days. Beetles were valuable prey for proteins and lipids compared to the alternatives. Termites and ants had equivalent contents of proteins, but termites were richer in lipids. Two monotypic diets composed of the main prey types (beetles and ants) had similar effects on fecundity and body mass compared to the mixed diet. Although termites have more lipids than ants and have a higher proportion of their biomass consumed, the monotypic diet of termites caused weight loss for spiders over time and reduced fecundity. Survivorship in all groups was similar. These results indicate that a diversified diet is not required for T. haemorrhoidale to achieve its maximum reproductive potential. This characteristic may be important to ensure the success of this species in colonizing and establishing large populations, even in disturbed habitats with low prey diversity.

Although courtship and mating behaviors have been described for nearly all scorpion lineages, intrasexual interactions in scorpions remain understudied. Recently, a novel ritualized behavioral unit, termed “arm-span competition,” in which individuals face off and extend their pedipalps laterally, was described from analyses of male-male contests in several scorpionid species. Here, we present the first documented observation of arm-span competition in a buthid scorpion, Tityus cf. rosenbergi Pocock, 1898. Interestingly, both T. cf. rosenbergi and most scorpionid species known to engage in arm-span competition exhibit a similar sexual dimorphism: males have markedly longer and more slender pedipalps than females. We suggest that the elongated pedipalps in males of these species might be the result of selective pressure related to ritualized arm-span competition. We also highlight the potential for citizen science to contribute rare observations to scientific literature.

A morphological study of the type material of two Colombian theraphosid species in the genus Thalerommata Ausserer, 1875, deposited in the European spider collections of the Natural History Museum, London, and Muséum national d'Histoire Naturelle, Paris, enables us to establish a new synonym: T. macella (Simon, 1903) is designated as a junior synonym of T. gracilis Ausserer, 1875.

Biomaterials are becoming increasingly popular in solving applied problems. Aciniform silk (wrapping silk) is one of the seven known types of silk secretions orb-web spiders produce. It has an impressive set of mechanical properties suggesting a high, hereto unexplored potential for textile and biomedical applications. Here we have summarized existing knowledge and identified the gaps in our understanding of the structure, functions, properties and biology of aciniform silk. Aciniform silk is composed of the protein aciniform spidroin (AcSp), which is characterized by relatively lower percentages of alanine and glycine than dragline silk. The specific mix of alpha helices and beta sheets is believed to bring about its great toughness and elasticity. The combination of high toughness and extensibility makes swathes of aciniform silk an ideal tool to keep the prey wrapped, but also for the protective encasing of spider egg clutches. Understanding of the relationship between the composition, properties and biological functions of aciniform silk is still rudimentary, as current studies are mostly mono-focal and barely apply an integrative approach. Closing this gap requires better integration of material science with ecological and evolutionary aspects. This will not only benefit a better understanding of why and how animals use silks, but it will also enable the production of better silk-inspired biomaterials with superior properties.