Detritus Camouflage in Webs ofHelvibis longicauda(Araneae: Theridiidae)

Predators and parasites of spiders attack eggs, spiderlings, juveniles, and adult spiders (Nielsen, 1923; Wise, 1993; Eberhard, 2000). In response to this selective pressure, spiders have evolved diverse defensive strategies (Foelix, 1996). The stabilimentum, a silken structure present in the webs of several orb-weaving spiders, probably serves as camouflage or predator distraction for young and adult spiders, and their egg sacs (Gertsch, 1949; Eberhard, 1973; Lubin, 1975; Herberstein et al., 2000). Other spiders incorporate prey carcasses, old and new egg sacs, and bits of debris into the silken stabilimentum of their orb-webs (Bristowe, 1958; Lubin, 1986; Herberstein et al., 2000), possibly to enhance the camouflage. The active addition of debris for camouflage in threedimensional webs has not previously been described for any spider species. I report here the presence of debris for camouflage on webs of the theridiid Helvibis longicauda Keyserling. The web of H. longicauda is built below an unmodified leaf that the spider uses as a retreat, resting near its lower surface. It consists of a mesh constructed with dry and sticky lines just under the leaf, and long, more or less vertical, sticky lines that extend downward from the mesh to other leaves (details of web in Gonzaga et al., 2006). These long lines are frequently interconnected by a few lines and have viscid globules along their entire length. Many webs have small pieces (3–7 mm long) of vegetation, such as bamboo leaves, tendrils, small flowers, and seeds attached to the mesh under the leaf retreat (pers. obs.) (Fig. 1).