Evaluation of Multiple Immersion Effects on Eggs From Haemagogus leucocelaenus, Haemagogus janthinomys, and Aedes albopictus (Diptera: Culicidae) Under Experimental Conditions.

Studies on the bioecology of Haemagogus leucocelaenus Dyar and Shannon 1924, Haemagogus janthinomys Dyar 1921, Aedes albopictus Skuse 1895 (Diptera: Culicidae) mosquitos are extremely important from an epidemiologic point of view, as they are known to be vectors of many important pathogens and, therefore, act as the main factor responsible for the maintenance of several zoonoses natural cycles. The present work aimed to elucidate their seasonal egg-hatching rate using the immersion method. Ovitraps were used to collect mosquito eggs from an Atlantic Forest fragment, in the State of Rio de Janeiro, Brazil, from November 2015 to November 2016. After collection, the eggs were immersed 40 times to assess their hatching rate and evaluate the number of immersions resulting in the highest hatchability during the study period. Differences in the proportion of hatched eggs between species and seasons (spring, summer, fall, winter) and in the numbers of immersions in which eggs hatched were assessed using odds ratios. Hg. leucocelaenus was the species with the highest number of eggs hatching in all sampling periods, followed by Ae. albopictus. Most Ae. albopictus eggs hatched on first immersion regardless of season. Both the numbers of eggs and the number of immersion in which the Haemagogus eggs hatched showed high variability within seasons. In spring, the proportion of eggs that hatched on the first compared to further immersions was similar, while in fall and winter a higher percentage (over 94%) of Hg. leucocelaenus eggs hatched on the first immersion; the opposite pattern was observed in the summer. These results differ from previous observations linking increased hatching to warmer months. The number of immersions in which Hg. leucocelaenus eggs hatched varied between seasons, however differences were not statistically significant. These results evidence the need for further studies to elucidate factors that influence hatching patterns.