Females of the melon fly, Zeugodacus cucurbitae (Diptera: Tephritidae), mate indiscriminately with males from a laboratory and wild strain

The melon fly, Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae), is a pest of many important cucurbit crops. The sterile insect technique (SIT) has been used to control the species and involves the release of mass-reared, sterile males to obtain matings with wild females. The ability of released males to compete successfully against wild males is key to the success of the SIT. Artificial selection acting under mass-rearing conditions may alter male behavior in ways that decrease acceptance by wild females. A pupal-color sexing strain of melon fly (termed T1) was developed in Hawaii, and males of this strain appear equal to wild males in mating competition. In the present study, trials conducted in both laboratory and field cages showed that T1 and wild females mate indiscriminately among T1 and wild males. Trials conducted in field cages also assessed the impact of two elements—overflooding ratio (i.e., ratio of mass-reared to wild males) and use of male-only vs. bisexual releases—on the mating success of T1 males. Observations of individual male–female pairs further revealed that the incidence of male mounting and the proportion of successful mounts (i.e., copulations) were independent of the strain identities of the paired flies.