Triatomine bugs search for vertebrate hosts to procure a blood meal and host odours mediate this behaviour. Perception of vertebrate odours occurs via an array of olfactory receptors in wall-pore and grooved-peg olfactory sensilla on the antennal flagellum. Electrophysiological recordings show that three of these receptors respond selectively to the host odour components nonanal, ammonia and isobutyric acid. Whereas nonanal causes increased displacement by the bugs, both ammonia and isobutyric acid attract triatomines walking on a servosphere. There is evidence for parsimony in the use of these semiochemicals in triatomines. As isobutyric acid occurs in the headspace of both Rhodnius prolixus and Triatoma infestans it may have an additional function as an aggregation stimulus in triatomines. Refuges occupied by triatomines are marked with their own faeces and are attractive to triatomines. Ammonia released from fresh faeces contributes to this attractivity. The bugs also perceive uric acid, a major constituent of their faeces, via receptors in a set of terminal pore gustatory sensilla on the distal flagellum of the antenna.

Index terms: Triatoma, Rhodnius, olfaction, gustation, behaviour

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