Identification of Predaceous Arthropods in Soybeans by Using Autoradiography 1

Abstract

Field cage experiments were conducted to identify predators which feed on eggs and early stage larvae of Heliothis spp., Pseudoplusia includens (Walker) and Anticarcia gemmatalis Hubner. Isotope labeled (32p) eggs, 1st-, 2nd-, and early 3rd-stage larvae were exposed to possible predators. Predaceous arthropods which obtained the label were identified by autoradiography. A total of 349 individual arthropods from 25 species obtained radioactive labels when exposed to lepidopterous eggs or early stage larvae. Major predators identified in this study were Nabis roseipennis Reuter, Geocoris punctipes (Say), and Oxyopes salticus Hentz. Nabis roseipennis was the most frequently labeled predator of eggs and larvae. Spider species encountered in this study were not labeled when eggs were provided as prey. A high percentage of the carabids found in the foliage such as Lebia analis Dejean, Callida decora (F.) and Colliuris pennsylvanicus (L.) was labeled. Other foliage dwelling beetles which contained the isotope were Coleomegilla maculata (DeGeer) adults and larvae and Notoxus monodon (F.). Several tettigoniids, Conocephalus fasciatus (Forster), also were labeled. Predation upon primary predators was demonstrated when labeled nymphs of G. punctipes and N. roseipennis were exposed to the indigenous predator complex.