*Department of Medical Parasitology, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT.
Odour movement, wind direction, and the problem of host-finding by tsetse flies
Article first published online: 13 MAR 2008
Volume 14, Issue 4, pages 369–380, December 1989
How to Cite
BRADY, J., GIBSON, G. and PACKER, M. J. (1989), Odour movement, wind direction, and the problem of host-finding by tsetse flies. Physiological Entomology, 14: 369–380. doi: 10.1111/j.1365-3032.1989.tb01105.x
- Issue published online: 13 MAR 2008
- Article first published online: 13 MAR 2008
- Accepted 28 February 1989
- Glossina, tsetse fly;
- odour plume;
- wind dynamics
ABSTRACT. Movement of host odour was modelled in natural tsetse habitats with smoke and ultra-light 7-cm-long wind vanes; the speed and direction of the air movements were analysed from video recordings thereof. Wind of <1 ms-1 did not move in straight lines, since large packets of air (>10 m across) often changed direction together. The rate of this change of direction (meander) correlated negatively with windspeed. In open woodland with a shrubby understorey (in which windspeed was reduced by a factor of >5 from that above the canopy, to ax 0.3 m s-1), this wind meander fell by 2d̀ s-1 change of direction for each 0.1 m s-1 increase in windspeed (r2=0.96). Over open ground without shrub cover, the meander fell by 0.5d̀ s-1 per 0.1 m s-1 increase in windspeed (r2=0.85). In both situations, such meandering virtually ceased in winds of > 1 m s-1. In woodland, the relationship between the direction of air movement near the surface of bare earth (one potential tsetse landing site) and that c. 0.5 m above ground level (flight height) was often weak (r2=0.2-0.4), but this problem would be reduced if the fly averaged the ground-level wind for at least 30 s. Odour (smoke) travelling from a source 15 m ‘upwind’ over open ground arrived at a notional tsetse fly for 80% of the time from a direction within 10d̀ of the true source direction. In typical tsetse woodland, however, the ‘odour’ arrived from all directions (including >90d̀ away from the source), with only a 30% bias towards the true source direction (±10d̀). Evidently, tsetse must navigate up odour plumes by means that get round these difficulties-simple, moth-type upwind anemotaxis alone seems unlikely to be adequate.