To reproduce, the entomopathogenic nematode Heterorhabditis bacteriophora (Oswego) needs to find, invade, and overcome the host immune response system. The initial host immune response is critical in determining the outcome of the interaction. We have shown that H. bacteriophora elicits a rapid cellular immune response and production of reactive oxygen species (ROS) in a resistant host, Manduca sexta. The nematode along with its symbiotic bacteria Photorabdus luminescens both have roles in overcoming the host defense. In this study we have characterized surface coat proteins from the nematode that we hypothesize are essential to evasion of the host cellular immune response. H. bacteriophora were reared in waxworms Galleria mellonella. Nematodes were washed extensively with sterile ultrapure water and then stored in sterile water to allow for regeneration of surface coat proteins. Storage water was previously found to inhibit ROS production by insect hemocytes. Proteins from storage water were concentrated and characterized by gel electrophoresis. These proteins do not cause proteolytic damage to hemocytes and are hypothesized to be antioxidant enzymes. We hypothesize these proteins allow nematodes to survive encapsulation. Nematode cuticular proteins were extracted in 10 M urea and characterized by two-dimensional electrophoresis. To determine the role of surface coat proteins in host evasion, the effects of these cuticular proteins were tested upon the in vitro encapsulation response of hemocytes from M. sexta and G. mellonella. Our data supports a role of these proteins in determining host suitability.