Mechanisms of adaptation to environmental stress in the pest species Locusta migratoria tibetensis Chen were investigated with respect to the effects of temperature and ultraviolet(UV) radiation on its antioxidant system.The effects of low temperature(5—20 ℃),high temperatures(30—45 ℃),and UV radiation on the activities of antioxidant enzymes and on the malondialdehyde(MDA) content of L.migratoria tibetensis adults were measured.At low temperatures,decreasing from 20 ℃ to 5 ℃,the activities of superoxide dismutase(SOD),peroxidase(POD),and catalase(CAT),and the MDA contents of the adult integument and alimentary canal all increased.The activities of SOD,POD and CAT also increased at high temperatures,increasing from 30 ℃ to 35 ℃.However,all enzyme activities decreased significantly when the temperature exceeded 35 ℃.The effects of radiation were examined at three wavelengths,ultraviolet-A(UV-A),ultraviolet-B(UV-B),and visible light.POD and CAT activities increased progressively during increasing exposure to radiation at all three wavelengths(the magnitudes of the changes were in the order: UV-B treatment UV-A treatment visible light treatment).UV-A and UV-B produced greater changes in the SOD activity of adult locusts than did visible light,during 24h and 72h exposures.Both UV-A and UV-B radiation caused a marked increase in the MDA content of the body wall,indicating a time-dependent induction of lipid peroxidation.Maximal contents of MDA were 0.72 nmol/g FW in the female integument,0.88 nmol/g FW in the female alimentary canal,0.66 nmol/g FW in male integument and 0.94 nmol/g FW in the male alimentary canal after exposures of 72 h UV-B,72 h UV-A,72 h UV-A,and 72 h UV-B,respectively.Thus,adult L.migratoria tibetensis are able to endure low temperatures(5—20 ℃) by protecting themselves from damage by reactive oxygen species but are unable to endure temperatures exceeding 35 ℃,which disturb the insects′ antioxidant enzyme system.The increased activities of antioxidant enzymes of L.migratoria tibetensis under UV-A and UV-B stress represent important adaptations to the environment of the Qinghai-Tibet Plateau,which is characterized by intense ultraviolet irradiation.