none Teratocytes are found in the hemolymph of Lygus hesperus Knight parasitized by Leiophron uniformis (Gahan). The chemical composition of these large cells and of hemolymph from parasitized and unparasitized hosts was determined. The composition of teratocytes when dried was mainly protein (38.07%), lipids (31.4%), carbohydrates (11.54%), and ash (2.47%). The teratocytes were 51% water. Hemolymph of parasitized L. hesperus contained lower protein and slightly lower lipid concentrations and higher sugar and % dissolved solids than hemolymph of unparasitized nymphs. Cytology; Biochemistry; Circulatory system; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Host parasite relationships Leiophron uniformis (Braconidae); Cell type; Chemical composition; Teratocytes in hemipteran host haemolymph; Hemipteran hosts; Lygus hesperus; Chemical composition of host haemolymph & of parasite teratocytes; Reaction of host to parasite; Lygus hesperus (Hemiptera), host haemolymph chemical composition Lygus hesperus (Miridae); Chemical composition, hymenopteran parasite effects; Haemolymph, effect of hymenopteran parasites; Hymenopteran parasites; Leiophron uniformis; Chemical composition of host haemolymph & of parasite teratocytes; Reaction of host to parasite; Leiophron uniformis (Hymenoptera), host haemolymph chemical composition