Predation by Argyrodes (Theridiidae) on Solitary and Communal Spiders

Species of Argyrodes Simon (Theridiidae) are best known as kleptoparasites in the webs of other spiders, particularly in the tropics (Exline 1945; Exline and Levi 1962; Kaston 1965; Vollrath 1976, 1978, 1979). They live in or near the webs of their hosts and take prey from the host's web. The methods used to take prey from the host vary for different species of Argyrodes and different host species. In some cases the Argyrodes take food which the host has left at the capture site or in the hub of the web. They may also take small trapped insects which are not normally used by the host (Robinson and Olazarri 1971). In other cases the kleptoparasites feed from prey while it is still in the jaws of the host spider (Robinson and Robinson 1973). Temperate zone Argyrodes are also found in the webs of other spiders, where they are generally considered to be commensal or kleptoparasitic. However, some temperate zone species of Argyrodes have been observed preying on their hosts. Argyrodes fictilium (Hentz) was observed feeding on an Araneus sp. host (Exline and Levi 1962) and on Frontinella communis (Hentz) (Archer 1946). Lamore (1958) reported A. trigonum (Hentz) feeding on Mecynogea lemniscata (Walckenaer) and Wise (in press) reports the results of an experimental study of the impact of A. trigonum on a population of Metepeira labyrinthea (Hentz.) It may be that predation on other spiders is more important than kleptoparasitism for some temperate Argyrodes. This note supports that view by presenting observations of spider predation by two species of Argyrodes, A. fictilium and A. baboquivari Exline and Levi. In addition it compares the occurrence and predatory activities of A.