Capture of mass-reared vs. wild-like males of Ceratitis capitata (Dipt., Tephritidae) in trimedlure-baited traps

The sterile insect technique (SIT) is widely used to suppress or eradicate infestations of the Mediterranean fruit fly, Ceratitis capitata (Wied.), an insect whose broad polyphagy poses a serious threat to fruit and vegetable crops. The SIT involves the production, sterilization and release of sterile insects to obtain sterile male by wild female matings, thus yielding infertile eggs. Mass-rearing over many generations is known to produce dramatic changes in the behaviour and life history of C. capitata. This study investigated the possibility that mass-rearing also alters male response to trimedlure, a sex-specific attractant widely used in detection and monitoring programmes. We compared captures of released males from a mass-reared strain and a recently established colony of wild flies in trimedlure-baited Jackson traps at three spatial scales - open field, large field enclosures (75 m²) and small field cages (7 m²) - in two separate years. In the first year, males were used independently of flight ability, while in the second year only males with demonstrated flight capability were used. Trap capture was scored 2 days after release for the open field and the large field enclosures but either 1 h or 1 day after release in the small field cages. The findings were consistent across these different experiments: wild-like males were captured in significantly greater numbers than mass-reared males in both years of study, except in the trials lasting 1 day in the small field cages where significantly more wild than mass-reared males were captured in 1 year but not the other. These results are compared with other studies, and their implications for SIT are discussed.