The Biology and Behavior of Triatoma Barberi (Hemiptera: Reduviidae) in Mexico: IV. Feeding and defecation patterns

The feeding and defecation behavior of Triatoma barberi , a widespread domiciliary vector of Chagas' disease in Mexico, was studied in 50 individuals each of all 5 nymphal instars and in both sexes of adults. The mean duration of feeding ranged from 10 min in lst-instar nymphs to 24 min in 5th-instar nymphs. The overall range varied from as little as 4 min to as long as 69 min. The percentage of bugs defecating during the blood meal was low in all stages. Overall, only 13% of the 350 bugs studied defecated during the blood meal, with 74% of these defecating during periods of interrupted feeding. None of the 50 males studied defecated during the blood meal. Postfeed defecation patterns indicated that 4th- and 5th-instar nymphs represent the greatest source of fecal contamination immediately after feeding, but they are surpassed by 2nd- and 3rd-instar nymphs between 3 min and 1 h following a blood meal. The mean time for a 1st defecation following feeding was late in all instars: 27 min for the 1st instar, 10 min for the 2nd, 8 min for the 3rd, 14 min for the 4th, 38 min for the 5th instar, 36 min for adult females, and 132 min for adult males. The greatest rate of fecal production occurred between 1 and 5 h after feeding. The poor vector efficiency of T. barberi with respect to the rapidity and frequency of defecations within a given time is undoubtedly the most important factor contributing to a low prevalence of infection with Trypanosoma cruzi in man, despite high rates of infection in the vector.