Response of the predatory mite, Amblyseius womersleyi (Acari: Phytoseiidae), toward herbivore-induced plant volatiles:: Variation in response between two local populations

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.