The Effectiveness of the Nest of a Desert Widow Spider, La Trodectus Revivensi & in Predator Deterrence

Most nocturnally-active arthropods rest during the day in concealed and protected locations. The nests or retreats of nocturnal spiders are often in vegetation or beneath stones. The widow spider Latrodectus revivensis of the Negev desert of Israel (Levy and Amitai 1983), builds a conspicuous, cone-shaped nest in bushes up to m high (Shulov 1948, Lubin et al. in prep.). The nest is attached by bridging threads to a horizontal capture platform, which in turn is attached to nearby stones or shrubs (Fig. 1). The most notable feature of the nest is the array of extraneous material, mainly arthropod carapaces, snail shells and feces, and dried plant material, placed on the outside. This material obscures the spider from view even in the early stages of nest construction when the dense silk layer of the upper portion of the cone (Fig. l) has not yet been laid down. There may be several functions of this layer of extraneous material, namely: (a) to shade the spider, and its eggs and young, from the high insolation experienced in the desert in summer, (b) to provide mechanical protection from predators by strengthening the nest, (c) to make the nest cryptic, (d) to obscure the spider from the gaze of predators. We have examined elsewhere (Lubin et al., in prep.) the function of the extraneous material on the nest in the regulation of temperature inside the nest. We found that this material plays a significant