Substance that Stimulates Host-Seeking by Microplitis croceipes (Hymenoptera: Braconidae), a Parasite of Heliothis Species1,2,3

Abstract

Frass of larvae of Heliothis sea (Boddie) (Lepidoptera: Noctuidae) elicited a host-seeking response by females of the Heliothis parasite, Microplitis croceipes (Cresson). The active material was present in the feces, salivary secretions, and hemolymph of host larvae, the hemolymph of pupae, and hemolymph and excretions of adults. The parasite's response to the stimulant varied considerably depending on the age and condition of the parasite. Water, ethyl ether, and methanol extracts of feces stimulated activity. Sephadex chromatography indicated that the molecular weight of the active material was in the order of 100–500. Responses equal to those from H. sea were elicited by feces of H. virescens (F.) and H. subflexa (Gueneé). Definite but considerably weaker responses were elicited by feces from larvae of Spodoptera frugiperda (J. E. Smith), S. exigua (Hübner), and Trichoplusia ni (Hübner); no response was obtained to feces of Cadra cantella (Walker) and Plodia interpunctella (Hübner).