Cross-induction of fruit acceptance by the medflyCeratitis capitata: The role of fruit size and chemistry

Abstract

Groups of female Mediterranean fruit flies, Ceratitis capitata(Wiedemann), were exposed for several days to one of three host fruit species. Oviposition-site acceptance behavior was subsequently assayed on five fruit species. Females accepted most often the fruit to which they were exposed. Females exposed to a small fruit, mock orange, accepted other fruit species less often as the size of the fruit increased; females exposed to a large fruit, sweet orange, accepted other fruit species more often as the size of the fruit increased. This tendency for experience with one host fruit species to alter differentially behavioral responses to alternative host fruit species has been defined as cross-induction. In contrast, females exposed to a medium fruit, kumquat, were not cross-induced: females accepted the medium fruit very often and rejected all other fruit species to approximately the same degree regardless of size. When females were exposed to small, medium, or large fruit and tested on spherical wax fruit models of a variety of sizes, patterns similar to those with real fruit were observed. Whereas naive females generally accepted a given model as frequently as real fruit of a similar size, experienced females generally accepted models much less frequently than real fruit. In a final experiment, females were exposed to different fruits and tested on spherical wax models treated with fruit chemicals. Experienced females generally accepted fruit-treated spheres more often than untreated spheres. In addition, females usually accepted most often models treated with chemicals from the fruit to which they were exposed. Two hypotheses about the mechanism by which experience alters fruit acceptance— termed the “sliding template” and “closing window” hypotheses— are presented. Results of fruit and model acceptance by naive and experienced females support the latter hypothesis.