Abstract
The insect immune reactions involve two types of responses i.e., humoral and cellular ones, whereby the overall immunity
results from a complex interaction of the two systems. In view of the cellular immune response, parasitoid venom has various
effects on host hemocytes depending on the host-parasitoid system. These include alterations in total (THC) and differential
hemocyte counts (DHCs), modifications in hemocyte morphology and ultrastructure, induction of hemocytic death and
inhibition of hemocyte spreading and encapsulation. The effects of parasitization and envenomation by ectoparasitoid, Bracon
hebetor Say (Hymenoptera, Braconidae) on total and differential hemocyte counts and hemocyte morphology of its host
Galleria mellonella Linnaeus (Lepidoptera, Pyralidae) 5th instar larvae were investigated. Five types of hemocytes i.e.
prohemocytes, oenocytoids, plasmatocytes, granulocytes and spherulocytes were observed in host hemolymph based on their
morphology. A significant decline was observed in total and differential hemocyte counts of the host exposed to parasitization
and artificial envenomation. In addition to that, parasitization has induced different morphological alterations in all hemocyte
types. These changes mainly include vacuolization in cytoplasm, loss of pseudopods, cell damage, loss of cell boundary and
cell membrane deformities. Our data reveals that parasitization has significant impact on cellular immune response of the host
which ultimately leads toward the death of the host insect. Therefore, venom of the B. hebetor has a strong potential to be
considered for the development of novel insect control tools for pest insects of diverse range of Pyralidae (Lepidoptera).
