Entomopathogenic nematodes are a group of nematodes (thread worms), causing death to insects. The term entomopathogenic has a Greek origin entomon, refers to insect, and pathogenic, which denotes causing disease. Although many other parasitic thread worms cause diseases in living organisms, entomopathogenic nematodes, are specific in only infecting insects. Entomopathogenic nematodes (EPNs) live parasitically inside the infected insect host, and so they are termed as endoparasitic. They infect many different types of insects living in the soil like the larval forms of moths, butterflies,flies and beetles as well as adult forms of grasshoppers and crickets. EPNs have been found in all over the world and a range of ecologically diverse habitats. The most commonly studied entomopathogenic nematodes are those that can be used in the biological control of harmful insects, the members of Steinernematidae and Heterorhabditidae (Gaugler 2006).