Vertical oviposition preference of Aedes albopictus (Skuse, 1895) (Diptera: Culicidae) at different heights and seasonal periods in an urban forest fragment in Manaus, Amazonas, Brazil

Mosquitoes of the genus Aedes Meigen, 1818 (Diptera: Culicidae) are important vectors of several arboviruses, including those that cause dengue, Zika, and chikungunya. Despite their epidemiological relevance, the vertical distribution of these species in large urban centers remains insufficiently documented. This study evaluated the vertical oviposition preference of Aedes albopictus (Skuse, 1895) at different heights during different seasonal periods. The research was conducted in a six-floor tower located within an urban forest fragment in Manaus, Brazil. The tower measured 15.13 m in height and 3.20 m at its base. Sampling was conducted at the following heights: ground level, 1.20 m, 2.50 m, 3.60 m, 4.90 m, 6.00 m, 7.30 m, 8.40 m, 9.70 m, and 10.80 m. Three ovitraps were installed at each height level, spaced 1.50 m apart, totaling 30 ovitraps per sampling. Monitoring was conducted daily over a 10-week period, with five weeks in the dry season and five weeks in the rainy season. The ovitrap positivity index and egg density index were used to compare population patterns among height levels and between seasons. Egg abundance was higher at lower heights. Relative humidity was positively associated with the mean number of eggs, particularly during the dry season. Although most eggs were recorded in the lower strata, their presence at higher levels indicates that Ae. albopictus is able to occupy elevated environments when conditions are suitable. These findings reinforce the need to consider vertical distribution in vector surveillance programs, especially in urban areas undergoing vertical expansion.