Abstract: 【Aim】 This study aims to compare the differences in demographic characteristics between susceptible and moderate spinetoram-resistant populations of Thrips hawaiiensis （Morgan）， and to make clear the resistance regularity and resistance risk of this insect to spinetoram， so as to clarify its disaster rule and to provide theoretical basis for its scientific control. 【Methods】 The resistant population was developed by spinetoram selection， and compared with the susceptible population by using the age-stage， two-sex life table. Moreover， the relative fitness (R_f) was calculated based on the intrinsic rate of increase. 【Results】 Compared with the susceptible population， the moderate spinetoram-resistant population had a longer duration of immature stages， shorter adult longevity and lower fecundity. The net reproductive rate R₀， intrinsic rate of increase r，  finite rate of increase λ， and mean generation time T for the spinetoram-resistant population were 44.12 offsprings， 0.1554 d^-1， 1.1681 d^-1， and 24.37 d， respectively， while those for the susceptible population were 56.96 offsprings， 0.1753 d^-1， 1.1916 d^-1， and 23.06 d， respectively. Based on the R₀ values， the relative fitness of the spinetoram-resistant population was 0.886. 【Conclusion】 This study revealed the biological fitness costs in T. hawaiiensis population with moderate resistance to spinetoram. It is suggested that the calculation of relative fitness should be based on the intrinsic rate of increase. Moreover， fitting the survival curve to Weibull distribution should be carried out with caution.

Key words: Thrips hawaiiensis, spinetoram, insecticide resistance, life table, fitness cost