none Heliothis virescens; HYMENOPTERAN-PARASITES; Cardiochiles nigriceps; Host regulatory protein secretion by parasite larvae & teratocytes Cardiochiles nigriceps; PROTEINS-; Regulatory factors secretion by larvae & teratocytes; EGG-; Teratocytes; LARVAL-DEVELOPMENT; Regulatory protein secretion; LEPIDOPTERAN-HOSTS; Heliothis virescens; Host regulatory protein secretion by parasite larvae & teratocytes Both larvae and teratocytes liberated upon hatching from the eggs of the endoparasitoid Cardiochiles nigriceps Viereck were found to release proteins into their surrounding environment as they develop. Teratocytes were found to synthesize and release a number of proteins into culture media in which they were incubated. The proteins released differed among the different teratocyte ages. Larvae were also found to release proteins into the culture media in which they were incubated. Ligation of the head or anal vesicle altered the protein pattern found in the media. The results demonstrate that both larvae and the associated teratocytes release proteins that may have important functions in the parasitoid-host interaction.