Preliminary study of the effects of wind velocities and wind shadows upon suction trap catches of mosquitoes (Diptera: Culicidae).

Abstract

Suction trap catches of mosquitoes on land were compared with catches from 2 traps placed on the main axis of a raft moored in the center of a 215 × 215-m water-filled borrow pit. Traps on the raft captured fewer females of Aedes, Anopheles, Coquillettidia, Culiseta, Psorophora, and Uranotaenia but greater numbers of Culex and Mansonia than traps on land. When a burlap-covered framework was erected that covered the raft and displaced the wind shadow from the downwind edge of the trap to the downwind edge of the raft, results were similar except that fewer Culex were captured on the raft than on land. Unlike females of most species, Culex females, and to a lesser extent females of Ps. columbiae, accumulated in the wind shelter and delayed their departure from the raft. Only upwind flight was indicated, whether winds were calm or greater than cruising flight speeds. Winds between 0.00 and 0.24 m/s had no discernable effect upon numbers of mosquitoes captured, but with winds between 0.25 and 0.49 m/s catches were reduced 75%. No evidence was found of downwind flight at any velocity. The inverse relation between wind velocity and the numbers of mosquitoes captured while flying over burlap appeared to be due to reduced flight activity rather than lower flight levels.