Effects of n-hexane, acetone and methanol extracts of Zygophyllum simplex L. and Trigonella foenum-graecum L. on Schistocerca gregaria (Forskal) 5^th nymphal instar were tested. Only n-hexane extracts of both plants showed that, biological toxic effects to S. gregaria nymphs. Mortalities percentages of 1000 ppm of Z. simplex and T. foenum-graecum n-hexane extracts to desert locust nymphs were 76.67 and 70.00 % after 8 days post treatment. Toxicity results indicated that, LD₅₀s of Z. simplex and T. foenum-graecum extracts were 2.04 and 3.16 µg/nymph, respectively. Also total carbohydrates, lipids, and proteinsin haemolymph of treated nymphs with 250 ppm, were reduced at days 2, 4, and 6 days post treatment. Thirty four and thirty eight phytochemical compounds were detected in n-hexane extracts of Z. simplex and T. foenum-graecum, respectively. Seventeen compounds were present in both plant extract.