Biology and ethology of Triatoma dimidiata (Latreille, 1811). I. Life cycle, amount of blood ingested, resistance of starvation, and size of adults.

Abstract

The life cycle of Triatoma dimidiata in the laboratory (at about 23°C and 75% RH) takes, as a mean, 11 months. This is reduced to about 8 months at a constant temperature of 26.5 + 0.5°C and 50 ± 5% RH. The cycle is probably considerably longer in nature, due to the very low aggressiveness of this species. Mean amount of blood ingested by the nymphs increases with the stadium and extreme mean values range from 4.5 mg for the first instar to 421.3 mg for the fifth. The values for the adults, based on 1 meal, vary from 141.0 to 290.4 mg for the male (mean: 220.0 mg) and 156.0 to 425.2 mg for the female (mean: 282.6 mg). The latter are more voracious than the males and can eat from 4105.4 to 9643.6 mg of blood during adulthood as compared with 952.3 to 5329.2 mg for the males. Starvation is resisted in direct relationship to the age of the nymphs. Insects fed once in a given instar survive considerably longer than those unfed. Maximum survival without a blood meal was 10-1/2 months for the fifth instar nymphs. Adults withstand starvation less well than fourth and fifth instar nymphs with no difference between males and females. Insects from the field and those reared in the laboratory represent different populations as far as the size of the adults are concerned. Mean values in length and width for females and males are respectively: 33.6 by 14.4 mm and 31.3 by 13.1 mm for those from the field, and 29.0 by 11.9 mm and 27.4 by 11.1 mm for the laboratory ones. This is attributed to more frequent feeding of the insects caught in the field.