Eggcase Construction and Further Observations on the Sexual Behavior of the Spider Sicarius (Araneae: Sicariidae)

Abstract

The eggcase of Sicarius is unique among spiders. Its masonry wall resembles in texture the nests of mud dauber wasps.. And, unlike other spider eggcases, it is buried in sand, attached to stones. We do not know of any other masonry construction by spiders, or of other buried eggsacs. Some spiders incorporate sand grains and detritus into their webs or their trapdoors. The European theridiid Achaearanea saxatile (C. L. Koch) makes a thimble-shaped retreat for herself and her silken eggsac (P6tzsch, 963), and covers the thimble with large sand grains and little stones. The colonial European zodariids, Zodarion germanicum (C. L. Koch) and Z. elegans Simon, build retreats under stones. Each semispherical retreat is covered by sand grains from the surroundings, and pieces of bark and spruce needles are woven into the wall. The retreat is used by the .spider and the eggsac is hung up in it. As far as I know, the building of the retreat has not been observed. Wiehle (1953) illustrates a row of large setae in front of the zodariid spinnerets and peculiar branched setae that cover the legs and tarsi. These seta.e are perhaps used for handling the detritus.

Convergent setal morphology in sand-covering spiders suggests a design principle for particle capture

“…The same may be true for Sicarius and Homalonychus, which both possess densely distributed setae (Chamberlin 1916;Roth 1984) with which fine particles associate ( Levi & Levi 1969;Roth 1984; figure 1). Previous descriptions of Sicarius and Homalonychus lead us to hypothesize that details of setal morphology provide the mechanism of sand capture and retention in these two genera.…”

“…Many arthropods that attach materials to their bodies hold them in place with specialized setae (Hö lldobler & Wilson 1986;Gorb 2001;Brandt & Mashberg 2002) that sometimes have elaborate microstructures (Hö lldobler & Wilson 1986). The same may be true for Sicarius and Homalonychus, which both possess densely distributed setae (Chamberlin 1916;Roth 1984) with which fine particles associate ( Levi & Levi 1969;Roth 1984; figure 1). Previous descriptions of Sicarius and Homalonychus lead us to hypothesize that details of setal morphology provide the mechanism of sand capture and retention in these two genera.…”

“…The materials attached range from bits of shell and algae to sand grains to the remains of dead prey (Cott 1957;Levi & Levi 1969;Vetter & Cokendolpher 2000;Brandt & Mashberg 2002;Eberhard 2003;Bruce et al 2004;Domínguez & Jiménez 2005). These materials often provide camouflage that facilitates predator avoidance or stealthy predation (Cott 1957;Hö lldobler & Wilson 1986;Eberhard 2003) but can also function to attract prey (Bruce et al 2004) and protect organisms from UV radiation (Adams 2001).…”

“…The incorporation of materials from the environment onto the body, dwellings, egg or larval cases has been observed in groups as diverse as arachnids, crustaceans, insects and echinoderms (Cott 1957;Levi & Levi 1969;Hö lldobler & Wilson 1986;Vetter & Cokendolpher 2000;Adams 2001;Brandt & Mashberg 2002;Eberhard 2003;Bruce et al 2004;Domínguez & Jiménez 2005). The materials attached range from bits of shell and algae to sand grains to the remains of dead prey (Cott 1957;Levi & Levi 1969;Vetter & Cokendolpher 2000;Brandt & Mashberg 2002;Eberhard 2003;Bruce et al 2004;Domínguez & Jiménez 2005). These materials often provide camouflage that facilitates predator avoidance or stealthy predation (Cott 1957;Hö lldobler & Wilson 1986;Eberhard 2003) but can also function to attract prey (Bruce et al 2004) and protect organisms from UV radiation (Adams 2001).…”

“…Most studies mentioning sand/dirt particle attachment are taxonomically focused, and the function of particle coverage is generally assumed to be camouflage. Though some aspects of the system have been investigated in Sicarius and Homalonychus (Reiskind 1965;Levi & Levi 1969;Roth 1984;Domínguez & Jiménez 2005), a detailed description of the mechanism of sand attachment has not been done for any taxon.…”