none Larvae of the tobacco budworm, Heliothis virescens (F.). parasitized by the braconid, Cardiochiles nigriceps Viereck, and comparable nonparasitized larvae were tested for susceptibility to methyl parathion and permethrin. Parasitized larvae were 14.2 times more susceptible than nonparasitized larvae to methyl parathion, and 2.5 times more susceptible to permethrin. The implications of these findings for the use of organophosphate and pyrethroid insecticides in integrated pest management programs are discussed.