Trichoplusia ni; PROTEINS-; Parasitism specific protein production by larva; LARVAL-DEVELOPMENT; Parasitism specific protein production & function, hymenopteran parasite; HYMENOPTERAN-PARASITES; Chelonus; Host larva parasitism specific protein production & characterization Chelonus; LEPIDOPTERAN-HOSTS; Trichoplusia ni; Host larva parasitism specific protein production & characterization Parasitization in insects brings about profound biochemical and physiological effects in the host which may include complete overriding of the normal endocrinological program, resulting in precocious metamorphosis and in blockage of pupal development. The subtle effects of parasitization include changes in the expression of hemolymph proteins and the appearance of proteins which are unique to parasitized hosts. One such protein has been identified in the hemolymph of Trichoplusia ni larvae parasitized by the braconid wasp Chelonus near curvimaculatus. In this study, purified preparations of the parasitism-specific protein were used to generate polyconal antibodies against the protein. Results from the immunocharacterization indicate the antibodies obtained are highly specific for the protein and are present in a high titer (1 :8000 antiserum dilution yielded strong signals in analysis of the protein in 0.25 microliter hemolymph). Subsequently, the expression of the parasitism-specific protein in the hemolymph and tissues was analyzed by immunoblotting during the entire course of development in normal and parasitized insects. The parasitism-specific protein was not detected in normal, unparasitized larvae. In parasitized insects, expression of the parasitism-specific protein appears to be stage-specific in that it is only detected during the last larval stadium of precociously metamorphosing larvae, but is absent from all earlier stages of development. none