Response of Selected Predator Species to Different Densities of Aphis gossypii1 and Heliothis virescens2 Eggs 3

Abstract

Four species of predators were each exposed to different densities of tobacco budworm, Heliothis virescens (F.), eggs in the presence or absence of the cotton aphid, Aphis gossypii Glover. When alternate prey (aphids) were absent, the functional response of most predators was usually directly proportional to the density, of Heliothis eggs. Under these conditions larvae of Hippodamia convergens Guerin-Meneville were the most effective predators, followed by adult lady beetles, Chrysopa carnea Stephens larvae, adult Geocoris punctipes (Say), and Orius insidiosus (Say), respectively. Among all predators except G. punctipes , total percentage consumption of Heliothis eggs was reduced when aphids were available as alternate prey. Geocoris and Hippodamia adults were least affected by the presence of aphids while Chrysopa and Hippodamia larvae were most affected. Interactions among the species were generally of a density-dependent nature.