The life and death of Hopkin's host selection principle

Hopkins' host-selection principle (HHSP) refers to the observation that many adult insects demonstrate a preference for the host species on which they themselves developed as larvae. The meaning of HHSP has changed significantly since its first proposal in 1916. This review considers how the meaning of HHSP has changed over time and considers the various mechanisms that could contribute to a behavioral bias for the developmental host. The assumption that HHSP implies that the behavior of adult insects is conditioned by larval experience has resulted in widespread condemnation of HHSP. Despite a great deal of attention, there is still very little convincing evidence for preimaginal conditioning of host choice in insects. But growing evidence indicates that genetic variation in behavior and conditioning during the life span of an adult insect can contribute to a preference for the host on which an insect developed. Insects can acquire adult oviposition or feeding preferences through exposure to chemical residues from the environment of earlier life history stages. The concepts of host races and host fidelity have become familiar and acceptable, while the association of HHSP with preimaginal conditioning has led to a general rejection of the term.