Abstract
We studied the response of two populations of the predatory mite, Amblyseius womersleyi, toward volatiles of kidney bean leaf infested by Tetranychus urticae in a Y-tube olfactometer. The predators collected in Kyoto (A . womersleyi-Kyoto) showed a significant preference for infested leaf volatiles to uninfested leaf volatiles, whereas the predators collected in Shizuoka (A . womersleyi-Shizuoka) did not. This difference was not due to a difference in their feeding experiences but to a genetic difference, since both populations were tested after being reared under the same laboratory conditions for more than three months (more than 10 generations) . We then compared the performance and behavior of the two populations. The fecundity and oviposition periods of A. womersleyi-Kyoto were not significantly different from those of A. womersleyi-Shizuoka. However, the dispersal of A. womersleyi-Kyoto from a T. urticae-infested bean leaf culture occurred earlier than that of A. womersleyi-Shizuoka. The lower dispersal ability in A. womersleyi-Shizuoka compared that of A. womersleyi-Kyoto is attributed to a difference in ability to distinguish infested plant volatiles from uninfested ones.
