Abstract: To explore the effects of acquisition of methidathion resistance on developmental duration and reproductive capacity, the developmental duration and reproductive capacity in the methidathion resistant strain (R-strain) and susceptible strain (S-strain) of the predacious mite Amblyseius womersleyi Schicha (Acari: Phytoseiidae) were studied at 25℃and 30℃in the laboratory. The results indicated that there were no significant differences in mating and oviposition behavior between R-strain and S-strain of A. womersleyi. The developmental duration, the oviposition period and peak, the number of eggs laid by one female in a day or during a generation, the egg hatching rate and the sexual ratio of R-strain were similar with these of S-strain. The results suggest that obtaining methidathion resistance has no obvious negative effects on the developmental duration and reproductive capacity of A. womersleyi.

Key words: Amblyseius womersleyi, methidathion, resistance, developmental duration, reproductive fitness