No. 2 — American Spiders of the Genus Argyrodes (Araneac, Theridiidae) By Harriet Exline x and Herbert W. Levi Spiders of the genus Argyrodes are mostly tropical and sub-tropical. Some, perhaps all, live as commensals in webs of larger spiders, especially in webs of Nephila clavipes (Linnaeus) and species of Gasteracantha and Argiope, and sometimes of Latro-dectus, Agelenopsis, Allepeira and others. Often large numbers of individuals, sometimes including more than one species, are found in the same host web. Twenty-three specimens including A. elevatus, A. cochleaforma and A. cordillera were collected from one Gasteracantha web near Banos, Ecuador (Exline, 1945). A pair of A. glooosus and a pair of A. cancellatus were collected by Exline in a web of Nephila clavipes near Donaldsonville, Louisiana, in 1959. Argyrodes usually feed on small insects in the host web, the small spiders and small insects apparently being unnoticed by the large host. However, Argyrodes have been ob-served a few times to prey on their hosts. Exline watched A. fictilium feed on its Araneus host, and Archer (1946) reported A. fictilium preying on Frontinella communis (Hentz) in Ala-bama. Lamore (1958) observed A. trigonum attack and feed on a host Allepeira lemniscata (Walckenaer). Argyrodes may live in host webs without constructing any web of their own, but often they add fine lines between the spirals of an orb-web, and occa-sionally they live independently, making their own small theri-diid webs. Argyrodes species hang in the web upside-down with the front pairs of legs folded. They are usually inconspicuous, resembling seeds, pieces of bark, or lichen accidentally attached to the web. When disturbed they jump, usually sideways, and drop, leaving a line attached to the resting place. Though the egg-cases are far more conspicuous than their makers, they are seldom preserved by collectors. They are beauti-fully constructed (Figs. 1-5) and are attached to the host web or to grasses or brush by strong threads. The shape is often characteristic. Urn-shaped cases are made by A. elevatus, A. caudatus, A. cancellatus (Fig. 5) and their relatives, and these l Mrs. D. L. Frizzell, Rolla, Missouri ; Research Associate, California Academy of Sciences.