Abstract
Some polyphagous herbivores prefer the host plants on which they developed. This enhances the genetic differentiation among populations on different host species, and thus they specialize on separate host species. The polyphagous spider mite Tetranychus kanzawai includes populations that have adapted to toxic plants such as Hydrangea macrophylla and Nerium indicum. We examined the influence of the host plants utilized during immature development of the mites on the host preference of adult females, in populations derived from H. macrophylla and N. indicum. When each population was reared on its original plant during the immature stage, they showed significantly higher preference for the original plant than when they were reared on Phaseolus vulgaris (suitable host). Thus, the preference for the host plant from which each population was derived is induced by exposure to the plant during the mite's immature development.
