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The desert plant, Lotus corniculatus (Fabaceae), inhabits the Saudi Arabian Sahara Desert. In these areas the desert locust, Schistocerca gregaria (Orthoptera, Acrididae), feeds on L. corniculatus containing the plant allelochemical linamarin; a cyanogenic glucoside that is usually toxic to polyphagous insects. Under laboratory conditions this plant was fed to S. gregaria. Haemo lymph proteins and allelochemicals detoxification in S. gregaria, fed on L. corniculatus were as sessed. Fe male 5th instar nymphs were reared on L. corniculatus or on wheat seedlings, Triticum aestivum, as control. In insects, glutathione-S-transferase is one of the most important detoxifying enzymes. The activity of glutathione-S-transferase (in units/gram) in the mid-gut tissues of 5th instar nymph females fed on L. corniculatus was significantly higher than in those fed on T. aestivum. The quantity of haemolymph proteins (in mg 100 mu l(-1)) in adult locust females resulting from nymphs fed on L. corniculatus was significantly less than it was in females fed on T. aestivum. Decreasing protein synthesis in the adult females of S. gregaria might be related to detoxifying toxic compounds in L. corniculatus.