none Heliothis virescens; LIPIDS-; PROTEINS-; Haemolymph composition changes, hymenopteran parasite development relations; HAEMOLYMPH-; Biochemical changes, synchronization of hymenopteran parasite development; HYMENOPTERAN-PARASITES; Cardiochiles nigriceps; Development, synchronization with changes in host haemolymph composition Cardiochiles nigriceps; LARVAL-DEVELOPMENT; Synchronization with changes in lepidopteran host haemolymph composition; LEPIDOPTERAN-HOSTS; Heliothis virescens; Development, synchronization with changes in host haemolymph composition Larval development of the parasitoid Cardiochiles nigriceps Viereck occurs in the last instar larva of its host, Heliothis virescens (F.). This allows the parasitoid to exploit the nutritional increase in the biosynthetic activity occurring in the host in preparation for metamorphosis. To understand the biochemical basis of this host parasitoid developmental synchrony, we undertook host ligation studies and analyzed host hemolymph for proteins and glycerol esters. Parasitization affected the biochemical profile of the host. The hemolymph protein concentration of parasitized last instar H. virescens larvae increased through time, whereas unparasitized (control) larvae were characterized by a decrease in the protein titer when they reached the prepupal stage. The effect of parasitism on glyceride titers of host hemolymph was not as pronounced as the effect on proteins. Ligation conducted on 5th instar hosts, which were parasitized as 4th instars, affected parasitoid development in a time-dependent way. The percentage of successfully developing C. nigriceps larvae increased with the increase of the time interval between parasitization and ligation. Ligation performed before day 2 of the 5th larval instar of H. virescens completely inhibited parasitoid development. Ligations that disrupted parasitoid development were associated with a low host hemolymph protein concentration. Parasitoid development was successful when hemolymph protein titer was high, as occurred when ligations were performed after day 3 of the 5th host instar in both control and parasitized larvae. Ligations in both situations resulted in a slight increase in glyceride titers. The results suggest that host proteins and/or some factor(s) associated with them may play a role in parasitoid growth and development.