ABSTRACT
Steinernema carpocapsae and Heterorhabditis bacteriophora and their respective bacterial symbionts, Xenorhabdus nematophilus and X. luminescens, although effective against a diversity of insect species, show considerable variation in strain efficacy. Insects exist in a myriad of environments where the potential for infection by microorganisms and parasites is great. In nonimmune insects the nonself-response components of the hemolymph consist of humoral factors and cellular factors. Plasmatocytes may be chemotactically attracted to granular cell-bacterial aggregates. The granular cells and plasmatocytes are the major effector cells of Lepidoptera, Coleoptera, and Diptera which participate in phagocytosis, nodule formation, and encapsulation. Lectins have been found in the hemolymph plasma and fat body and in and on hemocytes of many insects. The most salient attribute of the hemolymph of immune insects is a pronounced antibacterial activity. The bacteria eventually destroy the host’s hemocytes by releasing the hemocytotoxin, lipopolysaccharide, from the bacterial outer membrane into the hemolymph.
