VERTICAL-DISTRIBUTION OF ADULT MOSQUITOS (DIPTERA, CULICIDAE) IN SOUTHERN AND CENTRAL SWEDEN

The vertical distribution of adult mosquitoes was studied in southern (Norra Angstrom sum) and central Sweden (Tarnsjo) during August 1995, with an emphasis on the ornithophilic species Culiseta morsitans (Theo bald), Culex pipiens L., and Culex torrentium Martini. A modified slin gshot method was used to suspend Centers for Disease Control (CDC) min iature light traps, in combination with CO, as additional attractant, into the canopy of deciduous trees. Altogether 15,186 mosquitoes, incl uding 93 Cs. morsitans and 182 Cx. pipiens/torrentium, were collected at various heights above ground during 43 trap-nights. The numbers of Cs. morsitans and Cx. pipiens/torrentium per trap-night were not signi ficantly influenced by height, but the number of total mosquitoes per trap-night decreased with increasing height. Significantly larger prop ortions (alpha<0.001, chi-square test) of both Cs. morsitans and Cx. p ipiens/torrentium, to the total of other mosquitoes, were collected in the canopy than at chest height. The proportions of Cs. marsitans wer e 18% at 12 to 15.5 m and 2.2% at 1.5 m in Norra Angstrom sum, and 49% at 14 to 18 m and 0.6% at 1.5 m in Tarnsjo. The proportions of Cx. pi piens/torrentium were 36% at 12 to 15.5 m and 6.9% at 1.5 m in Norra A ngstrom sum, and 5.1% at 6 to 9m and 0.2% at 1.5 m in Tarnsjo. Our met hod of suspending traps in the canopy and use of a simplified protocol to quickly distinguish the relevant species was efficient for placing the traps and for sampling adult females of the ornithophilic species Cx. pipiens/torrentium and Cs. morsitans in Sweden. We suggest that t his procedure might also be of use to investigate these and other orni thophilic mosquitoes for bird-associated arboviruses in woodlands in t he European region.