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Orientation responses of the tomato fruit fly, Neoceratitis cyanescens, to visual and olfactory stimuli during host finding

Brévault T., Quilici S.. 1999. In : Rendon P. (ed.), De Galan A. (ed.). 3rd meeting of the working group on fruit flies of the western hemisphere. Guatemala City : MAGA, p. 86-86. Meeting of the Working Group on Fruit Flies of the Western Hemisphere. 3, 1999-07-04/1999-07-09, Guatemala City (Guatemala).

Behavioural responses of Neoceralitis cyanescens (Bezzi) (Diptera : Tephritidae) mature females to host fruit odor and fruit visual stimuli were, studied in a laboratory flight tunnel, Olfactory and visual stimuli were presented to individually released flies in wind conditions (30 cm/s) according to the following pattern : (1) fruit model with host fruit odor, (2) fruit model without host fruit odor, (3) only host fruit odor and (4) no stimulus. The effect of wind speed (0, 30 and 60 cm.s-1) and host fruit odor on the propensity to land on the fruit model was also tested. Host fruit odor was provided by green crushed fruits of bugweed (Solanum auriculatum Ait.) hidden behind a filter in the upwind end section of the tunnel. The fruit visual stimuli consisted in a bright orange sphere. Four main parameters were considered in assessing the fly's response : orientation on the release vial, mean time before leaving the release vial, percentage of flies that reached the upwind end section of the tunnel or landed on the sphere and mean time before landing on the sphere. In wind conditions, flies responded to the presence of host fruit odor alone by flying upwind to reach the upwind end section of the tunnel. When host fruit odor was combined to fruit model, the level of response did not significantly increase. Single fruit visual stimuli also elicited a positive response, but to a lower extent than when combined with host fruit odor. Actually, olfactory and visual stimuli appeared to act independently to elicit fly's upwind flight response. In the absence of host fruit odor, flies moved on the release vial to scan their environment. On the contrary, flies rapidly orientated toward wind borne odor and left the release vial sooner in the presence of host fruit odor. Host fruit odor increased the probability of alighting on the fruit model only in wind conditions, partially because response to fruit model alone was affected by wind. With host fruit odor, host finding required more time in windless than in windy conditions, originating from higher residence time on the release vial and/or non direct flights. Our results showed that olfactory information when carried by wind may significantly interact with visual stimuli during the fruit finding process at a short distance.
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