Interspecific competition among endoparasitoids of tobacco budworm larvae [Lep.: Noctuidae]

The ability of female larvae endoparasitoids [Microplitis croceipes Cresson:Cardiochiles nigriceps Viereck andCumpoletis sonorensis (Carlson)] to distinguish between unparasitized tobacco budworm,Heliothis virescens (F.), larvae andH. virescens larvae parasitized by the egg-larval parasitoidChelonus insularis,Cresson, was determined in laboratory studies. The 3 species of larval endoparasitoid females did not appear capable of distinguishing between unparasitized andC. insularis parasitized larvae resulting in multiple parasitoidism. The results of the ensuing competition between the 3 species for possession of the host demonstrated that bothC. sonorensis andM. croceipes were intrinsically superior toC. insularis. Both larva endoparasitoids destroyed the olderC. insularis larvae by physically attacking the latter. The presence ofC. insularis larvae in the host was found to prevent the hatch of compeatingC. nigriceps eggs through physiological suppression. The results show that the early attack of a host, as in the egg-larval parasitoid habit, is not necessarily advantageous.