Laboratory observations on the bionomics of Aedes fluviatilis (Lutz) (Diptera: Culicidae)

Abstract

AbstractA laboratory colony of Aedes fluviatilis (Lutz) was established in ambient conditions in Brazil in which temperature varied from 22 to 31°C and relative humidity from 61 to 73%. Females laid eggs 3–13 days (mean 5·6 days) after a blood-meal and produced, on average, 64·3 eggs per batch. Eggs were usually deposited directly on the surface of water and preferentially on water that had previously contained fourth-instar larvae. The eggs proved to have little resistance to desiccation, hatching rates being reduced when eggs were kept on dry filter paper for only 1–3 days. Hatching took place following the detachment of a cap-like portion of the anterior end or through an irregular longitudinal split along the side of the egg. In different experiments, about 10–20% of eggs failed to hatch. Eggs usually hatched 2 days after oviposition. The average length of larval life was 10·2 days, and the highest proportion of larvae pupated on day 9. The duration of the successive immature stages increased geometrically with age. Mortality was 1–2% in each of the first 3 larval instars but rose to about 10% in the fourth. In the larval stage, males developed more rapidly than females. Crowding lengthened the duration of the larval stage, reduced the numbers surviving to pupate and resulted in a disparate sex ratio with emergent males much more abundant than females. Pupation occurred throughout the day and night with a slight peak at 05.00–06.00 h. The pupal stage lasted 1–3 days, usually 2 days, and was the same in both sexes.