Behavioral Resistance to the Sterile Insect Technique by Mediterranean Fruit Fly (Diptera: Tephritidae) in Hawaii

A pilot test of the sterile insect technique (SIT) program against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), in coffee plantations in Hawaii failed after several years of continuous releases apparently, at least in part, because native C. capitata females from the treated area on Kauai altered their mating preferences and began rejecting most laboratory-reared males during courtship. In outdoor field cage experiments, females from other non-SIT Hawaiian islands did not change their mating preferences over the same period and accepted laboratory males 5–10 times more often than did resistant Kauai females. Two indices were devised to quantify the degrees of mating compatibility between laboratory-reared, sterilized flies and wild flies. The relative isolation index compares the numbers of homotypic (laboratory to laboratory or wild to wild) matings with heterotypic (laboratory to wild) matings, thus measuring the extent of departure from random mating conditions. The relative sterility index measures the proportion of wild females mating with laboratory males, thus providing a field cage level estimate of induced sterility. The results and implications of a series of field cage mating tests are discussed in the context of tephritid SIT programs worldwide.