Prey Size Preference of the American House Spider Parasteatoda tepidariorum

Abstract

The American House Spider (Parasteatoda tepidariorum) is commonly associated with human populations, and is a major predator of insects such as mosquitos and flies. Little is known about the prey preference of these spiders, for example, whether they prefer larger or smaller insects. This study examined prey size preference in P. tepidariorum, in an effort to both determine whether there is such a preference in these spiders, as well as whether that preference is for larger or smaller prey. Spiders were collected and placed into separate containers, in which they built webs. Prey insects were then collected, and classified as “large” or “small,” based on overall body length. Prey species was varied as much as possible, as to limit the effect of species preference on spider prey choice. The prey were kept alive in an attempt to best replicate natural prey choice conditions; as such, they were briefly cooled as to reduce their mobility prior to web placement. One small and one large insect were then simultaneously placed in the web, and prey choice was quantified. 110 trials were run. Through a chi-square analysis, it was determined that the spiders significantly preferred large prey insects over small ones. Several factors could be responsible for this finding, including more web vibrations from larger insects resulting in easier location, or a higher nutrition-to-effort ratio for larger insects. The study has many important implications, such as identifying selective pressures placed on both spiders and prey insects, as well as looking at the choice of spiders in a limited-nutrient environment, relevant to a possible future scenario faced by arachnids due to rapid climate change.