EFFECT OF EXPERIENCE ON HOST PREFERENCE IN CALLOSOBRUCHUS-MACULATUS (COLEOPTERA, BRUCHIDAE) - VARIABILITY AMONG POPULATIONS

Experiments using ''naive'' females established differences in host specificity among geographic strains of the seed beetle Callosobruchus maculatus; some females strongly preferred azuki bean over mung bean, and others failed to discriminate between the two hosts. We examined whether such congenital differences affect the degree to which host preference can be modified by experience. In choice tests, previous exposure to azuki bean increased the proportion of eggs laid on that host, but only in strains with a relatively low host specificity. Under more realistic, no-choice conditions, egg-laying experience affected oviposition rates mostly in strains with a high host specificity, but these experiments could not distinguish between the effects of a female's experience per se and her physiological state (i.e., egg load). Our results indicate that the likelihood of detecting an effect of experience on host choice depends on both the experimental protocol and the source of the test population. In natural populations of C. maculatus, recent egg-laying experience probably plays little or no role in discrimination between host species but may influence discrimination between conspecific seeds that differ in quality.