The effects of rearing conditions on the olfactory response of predatory mites, Phytoseiulus persimilis and Amblyseius womersleyi (Acari: Phytoseiidae)

We studied the effect of rearing conditions on the olfactory response of two predatory mite species, Phytoseiulus persimilis and Amblyseius womersleyi, to volatiles from kidney bean leaves infested by Tetranychus urticae in a Y-tube olfactometer. Mites of each species were reared under two different sets of conditions: (1) on an artificial arena (plastic board) onto which new T. urticae-infested bean leaves were periodically deposited, and (2) on a detached leaf culture. The mites of both species that had been reared in the artificial arena showed significant preferences for the infested leaf volatiles. A. womersleyi lost this preference one week after being transferred to the detached leaf culture, whereas P. persimilis maintained the preference for two weeks. In contrast, mites of both species that were reared on the detached leaf culture did not distinguish between the infested and uninfested leaf volatiles. However, once the mites were transferred to the artificial arena, both predator species preferred the infested leaf volatiles. This change in the olfactory response was significant in P. persimilis, while it was not in A. womersleyi. These results demonstrate that rearing conditions are important factors in determining the olfactory response of the two species of predatory mites.