Abstract: 【Aim】 Diurnal temperature fluctuation has very important influences on the development, survival, reproduction and longevity of insects. Previous researches have focused on constant temperature. The constant temperature design is unable to reflect the diurnal temperature fluctuation in the nature, and can not quantitatively analyze the difference between fluctuating and constant temperature. 【Methods】 We investigated the effects of different diurnal alternating temperature fluctuations with the same mean temperature (25±0℃, 25±2℃, 25±4℃, 25±6℃, 25±8℃, 25±10℃, 25±12℃) on life history parameters of different developmental stages in a worldwide cruciferous pest, the diamondback moth (DBM), Plutella xylostella. 【Results】 The results showed that different temperature fluctuations had significant effects on the development, survival, longevity and reproduction of  P. xylostella at different developmental stages. The life history parameters of P. xylostella at 25±2℃, 25±4℃ and 25±6℃ were similar with those at the constant temperature (25℃), but the fluctuating temperatures of 25±10℃ and 25±12℃ had significantly negative effects on the life history parameters of P. xylostella . 【Conclusion】 We found that wide diurnal temperature fluctuations have significant effects on P. xylostella, and suitable night low temperatures offset the disadvantage effects of daily high temperature stress on P. xylostella. Diurnal temperature fluctuation, as an important determinant influence factor of insects, should be considered into the predicting model of insect population dynamics, which will improve the accuracy of insect forecast in the field and really reflect the effects of diurnal temperature fluctuations on insect ecology.

Key words: Plutella xylostella, diurnal temperature, temperature fluctuation, development, reproduction, life history