Defense of oviposition sites by female oriental fruit flies (Diptera : Tephritidae)

Field observations revealed that females of the oriental fruit fly, Bactroc era dorsalis (Hendel), defended oviposition sites on mangos (Mangifera indi ca L.) against conspecific females. In most encounters, females simply lung ed at opponents and chased them off the fruit without physical contact. How ever, head-butting and pushing were observed in about 10% of the contests. Body size was a key determinant of fighting success, with larger females wi nning 85% of the encounters. In a field experiment, arrivals, oviposition, and aggression of females were compared between intact vs. sliced peaches. Similar numbers of females landed on the two classes of fruits, but a great er proportion of alighting females oviposited on sliced peaches than intact peaches. The adaptive function of female territoriality is discussed in li ght of these findings.