The role of the antennae in Triatoma infestans: Orientation towards thermal sources

The behaviour of Triatoma infestans (Hemiptera: Reduviidae) in response to thermal stimulation was studied, We analysed the effect of a heat source on the locomotion activity, and antennal movements of tethered insects, Antennal movements were studied both in the horizontal and vertical planes, and related to whether locomotion was being displayed or not, In addition, we analysed the trajectories of intact and unilaterally antennectomised insects towards a warm cylinder in a closed-loop design, In the presence of a thermal source, triatomine bugs performed more antennal movements and walked faster than in its absence, Insects displayed a sequence of walking bouts and standing phases of variable length, concomitant with active antennal movements in both the horizontal and vertical planes, While walking, the antennae moved smoothly in co-ordination. When the insects stopped, the movements changed dramatically, displaying abrupt changes of direction, The trajectories of control animals were straight towards the thermal source, Unilateral antennectomy resulted in deviated trajectories towards the goal, with the deviation always occurring towards the side of the intact antenna, The trajectories were fairly straight up to the moment of the extension of the proboscis, at a fixed distance of around 15 mm between the tip of the head and the warm surface, when a sharp body turn occurred, Control animals probed the source at a position perpendicular to the warm surface, Antennectomised animals missed the goal and probed the air at a position tangential to the surface of the warm body, The function of the antennae during the approach to a potential source of food, and the mechanisms of orientation possibly involved, are discussed. Copyright (C) 1996 Elsevier Science Ltd