DISPERSAL BEHAVIOR OF ADULT SNOW MELT MOSQUITOS IN THE UPPER RHINE VALLEY, GERMANY

The dispersal behavior of female snow melt mosquitoes was studied in-t wo forests in Rhineland-Palatinate, Germany, from April to August 1993 . Both CDC-light-traps and human bait collections were used to collect mosquitoes. Sampling sites were chosen along a west-east and a north- south transect in treated and untreated parts of a forest with a villa ge in its center. Around this settlement, breeding sites within a radi us of 1.5 to 2.5 km were treated. It could be shown that this buffer z one is sufficient to prevent a nuisance caused by snow melt mosquitoes in the village. The results lead to the conclusion that snow melt mos quitoes do not regularly migrate over large distances but stay near th eir breeding sites. In a detailed study of the behavior of Aedes rusti cus, it could be observed that these mosquitoes were resting in the in terior of the forest during daytime and leaving it with increasing dus k up to 50 m from the forest edge. A comparison of landing rate counts near a row of trees and in the open field showed higher activity near the row of trees indicating visual orientation of the mosquitoes. Alt hough the Ae. rusticus females left the forest regularly, no nuisance occurred in nearby villages. The treatment of breeding sites near sett lements appeared to be sufficient to prevent a nuisance caused by the snow melt mosquitoes.