Predation of the Isopod Crustacean Porcellio scaber by the Theridiid Spider Steatoda Grossa

Abstract

A population of the theridiid spider Steatoda giossa in Pacific Grove, California was studied to observe its predatory behavior towards the terrestrial isopod PorceUio scaber and subsidiary prey items. The isopod and spider are both found to be noctumally active. The carcasses of consumed prey are cut from the spider's web to collect in a debris pile which can be examined for an indication of long term dietary consumption. The isopod, though rejected as prey by most spiders because of repugnant tegumental glands, composes 84 percent of the diet of this spider as determined by web analysis. The spider from laboratory experiments was found to average 5.0 days between meals but able to tolerate periods of three weeks or more without feeding.