COMPARISON OF WALKING LOCOMOTORY REACTIONS OF 2 FORMS OF CALLOSOBRUCHUS-MACULATUS MALES SUBJECTED TO FEMALE SEX-PHEROMONE STIMULATION (COLEOPTERA, BRUCHIDAE)

A comparison of the walking locomotory reactions of flightless and fli ght form Callosobruchus maculatus males when subjected to an air curre nt scented with female sex pheromone was undertaken in a tubular olfac tometer. The pheromone was delivered to the males either as short puls es or as a continuous flow. To analyze the males' reactions, three beh avioral sequences were defined (sequence 1: male sensitivity/arousal; sequence 2: male reactivity; sequence 3: male progression and source l ocation). Although Rightless and flight form males were sensitive and reactive in all experiments, their locomotory displacement differed de pending on the stimulus conditions. The flightless form males' respons e remained roughly the same whatever the stimulus conditions (i.e., th ey always reached the pheromone source). In contrast, the flight form males displayed a markedly reduced response when subjected to a contin uous stimulation, indicating that intermittent on-off pheromone stimul ation is required in order to sustain their upwind walking progress. T his effect could be the result of sensory adaptation and/or habituatio n in the central nervous system of the flight form, requiring a flicke ring signal that is unnecessary for the flightless one.