Experiments with adult Rhodnius prolixus, carried out both in the laboratory as well as in a large-sized room, indicated the presence of a marked attracthn towards heat sources, activity reaching its peak around 99 degrees Fahrenheit. These studies also suggest that heatstimuli are effective over a certain distance. While infra-red radiation might be used by the sucking bug as a mean for orientation towards its prey, it is doubtful that heat is the only factor involved. Hopefully further studies will provide sufficient data for the construction ofelectric traps, for the practical purpose of vector control.