Dacus dorsalis flies can learn to find and accept host fruit

Mature oriental fruit fly females, Dacus dorsalis, from a population cultured on host fruit in the laboratory for one generation responded positively to visual and olfactory stimuli of individual natural kumquat (Fortunella japonica) and apple (Malus pumila) host fruit or models of these fruit hung from branches of potted trees in field enclosures. When females were exposed for 3 days to natural kumquats or apples on trees and subsequently released individually onto trees harboring one or the other of these fruit types, a significantly greater proportion of those exposed to kumquats than those exposed to apples or those not exposed to any fruit visited kumquats. Females exposed to kimquats for at least 3 days followed by at least 3 days of exposure to apples retained ability to find kumquats. Compared with females exposed to apples for 3 days or with naive females, females exposed to kumquats for 3 days exhibitied no less ability to find apples but did significantly refrain from accepting apples for oviposition. A final test was conducted in which females were exposed to natural kumquats or apples for 3 days and tested for response to inanimate models of either the same color and size as natural kumquats (orange, 20-mm diameter) or apples (green, 75-mm diameter) or models of the same color but opposite size. Results suggest that fruit size is the principal character learned and used in finding kumquats, which apparently are somewhat inconspicuous to an inexperienced foraging D. dorsalisfemale.