Factors affecting behavioural responses to visual stimuli in the tomato fruit fly, Neoceratitis cyanescens

Responses of Neoceratitis cyanescens (Bezzi) (Diptera: Tephritidae) females to visual stimuli were studied in a laboratory flight chamber. A bright orange sphere was used to investigate the effects of age, mating status and time of day on their responses. In no-choice assays, four parameters were considered: mean time before leaving the release vial, percentage of flies that visited the sphere, mean number of flights and mean time before landing on the sphere. Naive mated females first became strongly responsive to the orange sphere 6 days post-adult emergence (> 40%). The percentage of females that visited the sphere increased significantly with egg load. There were no significant differences in behavioural responses between virgin and mated mature females. In a choice situation between a yellow and an orange sphere, starved females displayed a greater propensity than well-fed females to land on the yellow sphere. Mature females were more responsive to the orange sphere when tested in the afternoon than earlier in the day. In a no-choice situation, females visited the yellow sphere as often as the orange sphere. However, the mean delay before landing was significantly greater for the yellow sphere. The results emphasize the importance of physiological condition on responses of N. cyanescens females to host-simulating visual stimuli.