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.

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.

Aunque se han descrito comportamientos de apareamiento para casi todos los linajes de escorpiones, las interacciones intrasexuales siguen poco estudiadas. Recientemente, a partir del análisis de luchas macho-macho en algunos escorpiónidos, se describió una nueva unidad de comportamiento ritualizado denominada “competencia por extensión de pedipalpos” en que los individuos se enfrentan extendiendo sus pedipalpos lateralmente. En este trabajo, presentamos la primera observación documentada de este comportamiento en un bútido, Tityus cf. rosenbergi Pocock, 1898. Tanto T. cf. rosenbergi como la mayoría de las especies de escorpionidos en que se describió este comportamiento, exhiben un dimorfismo sexual similar: los machos tienen pedipalpos notablemente más elongados y delgados que las hembras. Con esta observación, sugerimos que los pedipalpos de los machos en estas especies sean el resultado de la presión selectiva relacionada con la competencia ritualizada por extensión de pedipalpos. Además, enfatizamos el potencial de la ciencia ciudadana para contribuir con observaciones raras a la literatura científica.

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.

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.