The predatory behaviour of three reduviids, the millipede-feedingHaematorrhophus nigroviolaceus (Reuter) (Ectrichodiinae), the insectivorousPirates affinis Serville (Piratinae) and the haematophagousTriatoma rubrofasciata (De Geer) (Triatominae), both under natural and laboratory conditions, is discussed. Visual stimuli elicited by the moving prey appear important for the initiation of feeding response. The olfactory stimuli from the defensive secretions of the prey appear to enhance the response and help in the continuation of feeding. In the haematophagousTriatoma rubrofasciata, while feeding responses are elicited only by the temperature gradient around their vertebrate hosts, the visual and olfactory senses play only a minor role. On the basis of observations on feeding behaviour, appropriate predatory behaviour models for the three reduviid species have been constructed.