Abstract:Based on the observation of the development and reproduction of experi mental populations of alpharmethrin-resistant and susceptible Bactrocera dor salis strains at (28±2) ℃, the life tables of the populations were establish ed, and the differences in the relative ecological fitness of the two strains wa s analyzed. The results showed that comparing with alpharmethrin-susceptible B. dorsalis strain, the resistant one had longer durations of development st ages, average generation, and previposition, its fecundity was not stable and lo wer, and the hatch of eggs and the emergence of adults were depressed. The fecun dity of the susceptible and resistant strains was 3240 and 2407, respectivel y. Based on the life tables, the population trend index (I) of resistant str ain was 7910, while that of susceptible strain was 11697. The net reproducti on rate (R0) and the intrinsic rate of increase (rm) of resistant st rain were 141400 and 79463, while those of susceptible strain were 218400 and 83809, respectively. The relation fitness of resistant strain was only 06474. All of the results revealed that the resistant strain was at an obvious inferior position of reproduction and development.