Egg hatching dynamics and survival of immature stages of Aedes aegypti (Diptera: Culicidae) under field conditions during the cold season in Buenos Aires, Argentina

In temperate regions, the seasonal dynamics of Aedes aegypti (L.) (Diptera: Culicidae) is mainly influenced by temperature. It is assumed that, during the winter season, the population remains as eggs and that the development and population growth of surviving eggs begin during the following spring. The aim of the current study was to assess the temporal dynamics of egg hatching of Ae. aegypti during the winter in Buenos Aires city (Argentina), and analyze the survival of immature stages and their ability to complete development. The experiments consisted in immersing eggs and studying the development of immature stages of cohorts from June and September under natural conditions. The proportion of hatched eggs was compared between weeks of immersion and related to environmental variables. Survival was compared among cohorts and the development rate was related to the mean temperature during development. The results showed that, in general, egg hatching was over 50% during the whole winter period. The proportion of hatched eggs was positively associated with environmental variables. The immature stages completed the development during the cold season, with a trend towards increased survival of late-hatching cohorts. Survival was 30% at 13.2°C and above 90% at 20°C, whereas the development time at low temperatures was 49.4 days at 13.2°C, and 17.7 days at 20°C. The high hatching and survival observed throughout the cold season suggest that the local population might be benefiting from early hatching, by anticipating pupation and emergence of the first cohorts of adults in the early spring.