Do sympatric Trichogramma species parasitize the pest insect Helicoverpa armigera and the beneficial insect Chrysoperla carnea in different proportions?

Parasitism of two host species by five Trichogramma species (Hymenoptera, T richogrammatidae) was studied in the laboratory. The host species were: i) the bollworm Helicoverpa armigera Hubner (Lepidoptera, Noctuidae), an impor tant pest of many crops in the tropics and subtropics, and ii) one of its n atural enemies, the lacewing Chrysoperla carnea Stephens (Neuroptera, Chrys opidae), a predator often used as a biological control agent. The proportio n of H. armigera eggs parasitized from the total number of parasitized host s differed between Trichogramma species. The average number of parasitized eggs per female in 24 h by Trichogramma pintoi and T. bourarachae was 10 of H. armigera and about 0.5 of C. carnea. For the other three Trichogramma s pecies (T. cordubensis, T. evanescens and T. turkestanica) these averages v aried from 6 to 11 H. armigera eggs and from 3 to 4 C. carnea eggs. Total a dult offspring production, contacts with hosts, secondary clutch size and s ex-ratio of each Trichogramma species were determined as well. The results show that sympatric Trichogramma may parasitize target and non-target speci es in different proportions. If this difference corresponds to the field si tuation, simple laboratory tests could be performed to select not only effi cient biogical control agents, but also species which are the least detrime ntal to non-target hosts.