Orange‐derived stimuli regulating oviposition in the Mediterranean fruit fly

  Some visual and olfactory host stimuli influencing oviposition of the Mediterranean fruit fly ( Ceratitis capitata Wiedemann) in orange fruit were investigated in a laboratory‐reared strain of this species. Mated females of C. capitata were found to be attracted to the same extent by fragrant orange fruits and odourless sham oranges, while unmated females were notably less attracted than mated females by the above objects. Mated females laid significantly more eggs in orange‐coloured than in whitish (optically neutral) spherical wax dummies (diameter, 9.0 cm) as well as in both orange‐coloured and whitish wax dummies supplemented with high internal humidity (80–100%) compared with respective wax dummies supplied with low internal humidity (30–50%). The orange‐like colour together with high internal humidity provides basic stimuli supporting adequate oviposition of C. capitata in oranges. The oviposition rate of female C. capitata was not significantly changed when graded dosages ranging from 0.004 to 19.6  μ l of orange peel oil per cm 2 were added to orange‐coloured wax dummies, while oviposition was considerably subdued by addition of 3.9  μ l orange peel oil and completely disrupted by addition of 9.8 or 19.6  μ l of orange peel oil per cm 2 of whitish wax dummies. Oviposition of C. capitata in ripe orange fruit may thus be interpreted by the predilection of this tephritid species for an orange‐coloured, glossy pericarp, being capable of counteracting the deterrent effect of the essential oil found in orange flavedo.