Abstract: The western flower thrips, Frankliniella occidentalis (Pergande), is an invasive pest in China. Temperature is a key determinant for the stable establishment of thrips population in a new environment. In order to know the effects of temperature on the population growth of the western flower thrips, we investigated the development, survivorship and reproduction of F. occidentalis at different temperatures (15， 20， 25， 30 and 35℃), and calculated the parameters of population increase under different temperature conditions. The results indicated that the survivorship of F. occidentalis from egg-hatch to adult was the highest (62.8%) at 20℃, but no individual developed into adult at 35℃. The development rate increased significantly with rising temperature, the average developmental duration from egg to adult stage was about 30 d at 15℃, while the shortest was about 10 d at 30℃. The adult longevity was evidently shortened with rising temperature, at 15℃ the average lifespan was 36 d, the longest adult longevity even reached more than 60 d, while at 30℃ the shortest was only 10 d. The differences of fecundity (total number of the 1st instar nymphs produced by individual female) were not significant among 15, 20 and 25℃, with the values of 37.70, 32.56 and 37.80, respectively, which were all higher than that of the thrips at 30℃ (9.36 1st instar nymphs produced by individual female). The parameters of population growth ［the intrinsic rate of increase (r_m) and the net reproductive rate (R₀)］ were the highest at 25℃, with the values of 0.178 and 20.10 d^-1, respectively, while those at 15℃ were only 0.096 and 18.67 d^-1, respectively. From these results we concluded that temperature has great effect on the development of F. occidentalis, and the most suitable temperature range for this pest is 20-25℃, during which the intrinsic increase rate is higher. The development threshold temperature of F. occidentalis was estimated to be 7.4℃ and the effective accumulated temperature for development was 208.0 degreedays. In South China, Central China, North China and Northeast China, the estimated numbers of generations per year are 24-26, 16-18, 13-14 and 1-4, respectively, without consideration of other factors influencing the development and growth of the thrips. Especially in Kunming and Lijiang, Yunnan in Southwest China, the estimated number of generations per year are 13-15 and 8-10, respectively.

Key words: Frankliniella occidentalis, temperature, development threshold temperature, effective accumulated temperature, population growth, number of generations per year