The present work mainly focused on the susceptibility of Schistocerca gregaria (Forskal( 5^th instar nymphs to the entomopathogenic nematodes, Steinernema glaseri (Rhabditida: Steinernematidae) as a natural exposure experiment. The entomopathogenic nematode, S. glaseri turned out to be successful parasitoid of the orthopteran insect S.  gregaria. The death rate of locusts (sprayed with nematode on clover leafs) was remarkably high. Nematode killed approximately 65% of the locust with in 72 hours post infection at semi-field trial. The impact of parasitation on locusts' immune defense was closely investigated for S. gregaria parasitized by S. glaseri.  Nymphs died within 48-72h after being fed clover leafs contaminated with 1500/ml S. glaseri juveniles or previously contaminated with the dual cyclooxygenase/lipoxygenase inhibitor, phenidone. The injection of S. gregaria nymphs with, phenidone exhibited significant reduction in microaggegation in response to the nematode injections. At 12h post-injection, insignificant differences were recorded of the individual inhibitor on microaggregation, compared to the ethanol-treated (control) nymphs. Cellular defense components were strongly influenced by parasitation within the first 12h after injection of the nematodes.  Nymph's haemolymph was assayed.