Factors affecting the reproductive biology of Melittobia digitata and failure to meet the sex ratio predictions of Hamilton's local mate competition theory

Abstract

Abstract Melittobia digitata Dahms (Eulophidae, Tetrastichini), a species of parasitic wasp satisfying all of Hamilton's local mate competition requisites, does not exhibit the predicted change in sex ratio with increased foundress number. A multifactorial design was used to test how age, oviposition experience, feeding experience, mating, and foundress number affect host‐acceptance, number of offspring, and sex ratio of this species developing on honey bee pupae, Apis mellifera (L.) (Apidae, Apini). All factors significantly affected the time it took for oviposition to commence. Females oviposited soonest when they were 2 days old, mated, had previous feeding and oviposition experience, and were placed on hosts with multiple foundresses. Although the age difference between 2‐ and 5‐day‐old females is small, it significantly affected reproductive behavior. Age, mating, and foundress number were found to have an effect on sex ratio, however, the foundress effect was found to be a mathematical artifact of the limited host size. After correcting for this variable, females were found to have a constant sex ratio of approximately 0.05. Several 2‐way interactions between factors were revealed: age and experience, age and foundress number, age and mating, foundress number and experience, and foundress number and mating. One 3‐way interaction was found between age, mating, and foundress number. This study demonstrates that the sex ratio of M. digitata is not altered with increased foundresses, as predicted by Hamilton, and that slight changes in preconditioning may modify reproductive behavior.