The early second instar (8 days after parasitization) larvae of Toxoneuron nigriceps were incubated in the artificial rearing media supplemented with unparasitized and parasitized hemolymph of the host, Heliothis virescens. The growth (increase in length and width), development (molting), and survival of the incubated larvae were observed. The incubated second instar parasitoid larvae grew well and molted to third instars. The semisolid form of the rearing media promoted better development than the liquid form. Some of the in vitro reared third instar T. nigriceps larvae demonstrated behavioral changes that could be expressed as the preparation for cocoon formation or pupation.However neither a cocoon nor pupation occurred.