On the nature of learning in oviposition site acceptance by apple maggot flies

In a previous study, we found that after a female apple maggot fly, Rhagoletis pomonella, had arrived on a host fruit, its propensity to accept (bore into) or reject that fruit prior to egg deposition was modifiable through experience, and hence involved learning. Here, we aimed to determine whether the true nature of the learned response was either (a) one in which a conditioned female, as a result of having become familiar with a particular fruit type, formed a greater propensity to accept that type in a future encounter than had a naive female, or (b) one in which a conditioned female formed no greater propensity to accept a particular fruit type but simply was less prone than a naive female to accept a novel fruit type. The results of two experiments supported the latter mechanism, while the results of a third experiment provided evidence for both mechanisms. The possible adaptive significance of learning to refuse a novel resource type is discussed.