DEVELOPMENTAL BIOLOGY AND MORPHOLOGY OF PERISTENUS-DIGONEUTIS LOAN (HYMENOPTERA, BRACONIDAE, EUPHORINAE)

Peristenus digoneutis is a larval parasitoid that has been introduced from Europe and is now established in New Jersey as a biological control agent against the tarnished plant bug Lygus lineolaris, in alfalfa. The evaluation of its impact on indigenous species requires the identification of its immature stages to species level. Specimens of each stage of development of P. digoneutis were obtained by dissecting parasitized tarnished plant bug nymphs in the laboratory. The mirid nymphs were individually reared on green bean, Phaseolus vulgaris L., at 21 +/- 1 degrees C, 18:6, to cover the entire development of all immature stages of the parasitoid. The egg matures in 5 days. There are three larval stadia, the first two molting inside the host while the third emerges from the host. The first instar lasts 8 days, the second at least 4 days, and the third lasts a few hours before exiting the host. In a cocoon spun by the final instar, the pupa develops for 2 weeks followed by the preimago, which enters diapause for a period of about 8 months in the case of second-generation individuals. The mouth sclerites of the final instar larvae of P. digoneutis, P. pallipes, and P. pseudopallipes are not reliable distinguishing characters. The adult characters of the preimaginal stage, however, can be used to distinguish the exotic P. digoneutis from the two native species. (C) 1995 Academic Press, Inc.