The height and direction of flight of mosquitoes in West African savanna, in relation to wind speed and direction

The height and direction of mosquito flight related to wind speed and direction, in the absence of a host, was investigated in open savanna in The Gambia, West Africa. Non-directional suction traps (at heigts of 0·68, 2·13 and 3·15 m); directional flight traps facing four directions ar three levels (0·00–1·37 m, 1·45–2·82 m and 2·90–4·27 m) and directional suction traps facing two directions at three heights (0–1·2 m, 2·4–3·7 m nd 4·9–6·1 m) were used. Catches form the non-directional suction traps and pooled data from all flight traps at each level showed an inverse relationship between wind speed and the height of flight ofAnopheles melas(Theo.), of gravid females and of male mosquitoes. There was no indication of a similar relationship for theCulex decensTheo. group or forC. thalassiusTheo. The results from flight traps and directional suction traps showed that all mosquitoes were apparently flying upwind at all the levels investigaed. It is concluded that, although upwind flight probably does not occur naturally in the open at eights of more than 1 or 2 m, these experiments indicate that upwind flight could occur at higher levels, in the lee of tree and other obstacles.