Herbivore host plant selection: whitefly learns to avoid host plants that harbour predators of her offspring.

Evidence is accumulating that herbivorous arthropods do not simply select host plants based on their quality, but also on the predation risk associated with different host plants. It has been suggested that herbivores exclude plant species with high predation risk from their host range. This assumes a constant, predictable predation risk as well as a rather static behaviour on the part of the herbivore; plants are ignored irrespective of the actual predation risk. We show that adult females of a small herbivore, the whitefly Bemisia tabaci, can learn to avoid plants with predatory mites that attack only juvenile whiteflies, while they accept host plants of the same species without predators. Predatory mites disperse more slowly than whiteflies; they cannot fly and walk from plant to plant. Hence, by avoiding plants with predators, the whiteflies create a temporary refuge for their offspring. We suggest that the experience of arthropod herbivores with risks associated with host plants plays an important role in their host plant selection.