Experiments were carried out on the penultimate and last larval instars as well as newly emerged adults of Schistocerca gregaria. treated orally with antibodies, which have been reared germ-free to adult should tend towards the solitary end of the phase spectrum, started with loss of colour melanin; the reduction significantly was 85.63%. The potential of this parameter as a monitoring tool of phase transformation in the desert locust. Metabolic rate measurements applied at the mature adult life around day 15 alter fledging for both two phases solitary and gregarious locusts. Indicated that significantly increase for synthesis with solitary phase especially protein, where it reached 39.19 and 24.08% for male and female, respectively. But in the same time induced non-significant changes in lipids and carbohydrates energy reserves, the target for adi­pokinetic hormones that make energy more available, they were higher in gregarious than in solitary locusts. Curiously, in the light of this situation, parallels exist between two hosts in metabolic energy reserves and reproductive potential of the nematode Steinernema carpocapsae. The results obviously indicated that, reduction in reproduction potential of nematodes Inside solitary lo­cust host for about 68.43 and 74.03% for male and female, respective­ly. They were approximately three times for male and four times for fe­males. The hypothesis suggested that the gut flora related to Schistocerca gregaria may benefit pathogenic microorganisms such as S carpocapsae nematode culture.