AbstractInvestigations were conducted to determine the titer of storage proteins in larvae of the cabbage looper,Trichoplusia ni(Hübner), that were parasitized by the ectoparasitoidEuplectrus comstockiiHoward (Hymenoptera: Eulophidae). A gradual increase was noted in the titer of the storage proteins present in the hemolymph of parasitized third and fourth instar larvae and in the hemolymph of isolated thoracic and abdominal tissues of fourth instar larvae. The final amount present in parasitized third and fourth instar larvae was similar to that found in nonparasitized fifth instar larvae. The stimulation of storage proteins in envenomed larvae demonstrates the ability (competence) of early larval stages to produce a gene product that normally occurs in the last larval stadium of the lepidopteran larval host. The gene expression necessary for storage protein production in isolated tissues may be altered by mechanisms separate from inherent developmental processes and the intact endocrine system. © 1994 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United States of Amer