Extremely High Biting Densities of Aedes albopictus (Skuse) (Diptera: Culicidae) at a University Campus in Nagasaki, Japan

Aedes albopictus (Skuse) transmits several arboviral diseases. This mosquito was the vector responsible for both the past and recent dengue outbreaks in Japan. Sites with a high density of A. albopictus are at risk of outbreaks of arboviral diseases. This study describes extremely high biting densities of A. albopictus at a campus of Nagasaki University, southwestern Japan. In August of 2015 and 2016, an 8 min human-bait-sweep collection obtained on average 33.4 and 38.9 females, respectively. In both 2015 and 2016, the highest and the second highest biting densities were observed at sites densely shaded by trees and covered with a large number of understory plants. In addition, major A. albopictus breeding sites were identified near these locations in 2016. A predaceous larval mosquito, Lutzia vorax Edwards, appeared to strongly suppress the breeding of A. albopictus in catch basins near the site with the highest adult density, although its effect was insufficient to maintain A. albopictus density at a low level. After the catch basins had been cleaned, A. albopictus immatures became more abundant, especially in shallow catch basins in shaded sites.