none Heliothis virescens; WEIGHT-; HEAD-; Head capsule development; PROTEINS-; Haemolymph protein level; FEEDING-RATE; HAEMOLYMPH-; Protein level; HAEMOCYTES-; Cell counts; EXCRETION-; Hymenopteran parasite effect; LARVAL-DEVELOPMENT; Head capsule, effect of hymenopteran parasite; HYMENOPTERAN-PARASITES; Cardiochiles nigriceps; Host development & physiology, effect of parasitism Cardiochiles nigriceps; LEPIDOPTERAN-HOSTS; Heliothis virescens; Host development & physiology, effect of parasitism Cardiochiles nigriceps Viereck is an important parasite of the tobacco budworm Heliothis virescens (F.). The parasite is distributed in the Southern and South Eastern regions of North America and is primarily associated with H. virescens on most host plants. Parasitism of H. virescens by C. nigriceps resulted in a slight reduction of the head capsule measurements of the host larvae (three, six, ten and thirteen days old) after parasitization, when compared with the non-parasitized larvae (control).There was also a reduction of the total hemocyte counts of three and six days old larvae after natural parasitization as compared with teratocyte injected larvae and non-parasitized ones. The physiological and biochemical changes that occur in the larvae after parasitism were described. These included changes in weight, feeding, excretion and changes in haemolymph protein. The sources of the factors that may elicit such changes was discussed. The role of the adult female, her progeny and associated teratocytes were explained.