Demolition of a rural house in the State of Cojedes, Venezuela, provided a collection of 7.934 Rhodnius prolixus of which a random sample of 1,415 was weighed within 48 hours. The field weights, coupled with laboratory information of weight loss (in %) with time, average blood ingestion and meal size sufficient to promote moulting, were used to estimate biting rate under domiciliary conditions. The results show that in this particularly highly infested house, the R. prolixus population bites, on the average, at a rate of 58 times/person/day, draining blood at a rate of about 100 cm3/person/month; this meant a total of 1.2 litres/month from the 11 people inhabiting the house. It was found that the more advanced R. prolixus is in its development, the more aggressive it is in securing its meal: 15, 25, 30, 59 and 77% of fed insects of instar 1 through 5, respectively, were able to achieve moulting with only one meal. Applying the estimated biting rate to R. prolixus collections of other 13 demolished houses, with more typical insect population densities, an average biting rate of 9 bites/person/day was obtained; this value was, however, extremely variable, ranging from 0.2 bites/person/day (once every five days) to 33 bites/person/day.