ORIENTED RESPONSES OF THE TRIATOMINE BUGS RHODNIUS-PROLIXUS AND TRIATOMA-INFESTANS TO VERTEBRATE ODORS ON A SERVOSPHERE

Oriented responses of both R. prolixus and T. infestans adults were re corded on a servosphere to mouse-odour, one of its components (CO2), a nd to rabbit urine-odour. The volatiles were delivered in an air-strea m under controlled conditions which excluded other sensory modalities. In stimulus-free air the triatomines walked preferentially downwind i n straight bouts interrupted by stops or periods at relatively low spe eds, all of variable duration. In odour-laden air, bugs maintained the ir typical walking habit but switched fram negative to positive anemot axis. The characteristic response to odour onset was to stop, sample t he air with the antennae, turn upwind in situ, and then walk off in th e direction of the source for at least a few seconds, i.e., odour medi ated anemotaxis. Mouse-odour caused T. infestans to increase its speed to 5.3 cms(-1). Both species continued with the upwind response for s ome time after odour delivery ceased, but the crosswind component of t he tracks was more prominent during this period-an effort, we presume, by the bugs to re-contact an odour plume. This investigation provides unequivocal evidence for host finding in triatomines by olfactory cue s alone.