Shaped by the Sun: the effect of exposure to sunlight on the evolution of spider bodies.

Body temperature can strongly influence fitness. Some Sun-exposed ectotherms thermoregulate by adjusting body posture according to the Sun's position. In these species, body elongation should reduce the risk of heat stress by allowing the exposure of a smaller body area to sunlight. Therefore, selection should favour more elongated bodies in Sun-exposed than in Sun-protected species. Diurnal orb-web spider species that sit on their webs are more likely to be Sun-exposed, on average, than nocturnal or diurnal shelter-building species. We measured the body elongation of orb-web spiders (Araneae, Araneidae) across 1024 species and classified them as Sun-protected or exposed based on the literature. We found that Sun-exposed species evolved more elongate bodies than Sun-protected ones. Further, we built a model combining traditional heat transfer models with models of thermoregulatory postures in orb-web spiders and meteorological data. The model indicates that body elongation in large orb-web spiders decreases the risk of high body temperatures. Overall, our results suggest that Sun exposure influenced the evolution of body shapes of orb-web spiders.

The more, the merrier: a new colonial species of the orb weaving spider genus Leucauge White, 1841 (Araneae: Tetragnathidae) from the Amazon rainforest.

A new Leucauge species, widespread in the Amazon rainforest, is described and illustrated. Leucauge behemoth n. sp. lives in colonies, usually positioned above turbulent waters. Both males and females have a unique color pattern, especially on the abdomen, which makes this species easily identifiable. Males are distinguished from most congeners by the long hook of the cymbium and from their closest relatives by the lack of a cymbial dorsobasal process. Females of this species differ from their congeners by the presence of a rounded ventral process in the epigynum. Leucauge argyroaffins Soares & Camargo, 1948 is proposed as a junior synonym of Leucauge argyra (Walckenaer, 1841).

Diagnostic notes on the spider orb-weaving genera Carepalxis and Ocrepeira (Araneae: Araneidae), with description of three new species from Central Brazil.

Three new species of the araneid spider genera Carepalxis L. Koch, 1872 and Ocrepeira Marx, 1883 from Central Brazil are described and illustrated: Carepalxis topazio new species, based on a single female from Cristalina; C. quasimodo new species, from Braslia and Jaborandi based on females and a male, this being the first male of Carepalxis described in the American continent; and Ocrepeira planalto new species, based on males and females from Cavalcante, Cristalina, Jaborandi and Alto Paraso. A key to Carepalxis females in the New World is provided. Furthermore, the similarity between American Carepalxis and Ocrepeira is discussed, with diagnostic considerations.