Hostname: page-component-7c8c6479df-fqc5m Total loading time: 0 Render date: 2024-03-28T17:17:47.283Z Has data issue: false hasContentIssue false

Odour plume shape and host finding by tsetse

Published online by Cambridge University Press:  19 September 2011

John Brady
Affiliation:
Department of Pure and Applied Biology, Imperial College of Science, Technology and Medicine, Silwood Park, Ascot, SL5 7PY, UK
M. J. Packer
Affiliation:
Department of Pure and Applied Biology, Imperial College of Science, Technology and Medicine, Silwood Park, Ascot, SL5 7PY, UK
Gabriella Gibson
Affiliation:
Department of Pure and Applied Biology, Imperial College of Science, Technology and Medicine, Silwood Park, Ascot, SL5 7PY, UK
Get access

Abstract

Plotting the movement of air through typical tsetse habitats in Zimbabwe revealed that it is liable to change direction by over 90° within a few metres. In winds of < 1 m/sec, there was a negative correlation between windspeed and the wind's tendency to meander, whether in thick bush or out in the open. And at the mean windspeed of wet season mopane woodland (0.3 m/sec), the wind changed direction by c. 15°/sec. Accordingly, host odour does not move downwind in simple trajectories that tsetse flies could easily follow. Even 5 m from a source, odour (modelled with smoke) approached a notional tsetse fly for a quarter of the time from >90° away from the true source direction. Also, air turbulence at common tsetse resting sites generates much nonsense information about the “true” direction of any odour-bearing wind. The suggested answer to how tsetse manage to find distant, invisible hosts, in spite of this confusing information from the wind, is that they progress by a biased random walk which is the outcome of their upwind anemotactic responses to odour-bearing wind and the proportion of the time for which the wind does blow in the “correct” direction. Computer simulation shows that this might work in principle.

Résumé

L'analyse du mouvement de l'air dans des habitats typiques de tsé-tsé au Zimbabwe rèvèle que celui-ci est susceptible de changer de direction de plus de 90° sur quelques mètres. Dans le cas de vents <1 m/sec, une corrélation négative est observée entre la vitesse du vent et sa tendance à sinuer, que ce soit en brousse épaisse ou en terrain dégagé. Pour la vitesse moyenne du vent dans les bois de mopanés en saison des pluies (0.3 m/sec), le vent change de direction de 15°/sec. Conséquemment, l'odeur de I'hôte au fil du vent ne se déplace pas en trajectoires simples que les tsé-tsé pourraient suivre facilement. Même à 5 mètres d'une source d';odeur, celle-ci (modélisée par de la fumée) approche une mouche tsé-tsé imaginaire avec un écart de plus de 90dig; par rapport à la direction exacté pendant le quart du temps mesure. De plus, les turbulences dans lesgitesde repos habituelsdes tsé-tsé génèrent beaucoup d'information erronée (“non-sens”) sur la “vraie” direction des vents porteurs d'odeurs. A la question de savoir comment les simulies réussissent à trouver des nôtes invisibles à distance malgré cette information déroutante, les auteurs suggèrent une progression au hasard biaisée, résultat de leurs réponses anémotactiques vers le vent porteur d'odeurs d'une part, et de la proportion de temps pendant iaquelle le vent souffle dans la “bonne” direction d'autre part. La simulation par ordinateur montre que ce schéma peut marcher dans le principe.

Type
Research Article
Copyright
Copyright © ICIPE 1990

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Brady, J. (1988) The circadian organization of behavior: timekeeping in the tsetse fly, a model system. Adv. Study Behav. 18, 153191.CrossRefGoogle Scholar
Brady, J., Gibson, G. and Packer, M. J. (1990) Odour movement, wind direction, and the problem of host-finding by tsetse flies. Physiol. Entomol. 14, 369380.CrossRefGoogle Scholar
Bursell, E. (1984) Effects of host odour on the behaviour of tsetse. Insect Sci. Applic. 5, 345349.Google Scholar
Bursell, E. (1987) The effect of wind-borne odours on the direction of flight in tsetse flies, Glossina spp. Physiol. Entomol. 12, 149156.CrossRefGoogle Scholar
Bursell, E. and Taylor, P. (1980) An energy budget for Glossina (Diptera: Glossinidae). Bull, entomol. Res. 70, 187196.Google Scholar
Businger, J. A. (1975) Aerodynamics of vegetated surfaces. Heat and Mass Transfer in the Biosphere vol. 1 (Edited by deVries, D. A. and Afgan, N. H.), pp. 139165. John Wiley, New York and London.Google Scholar
Colvin, J., Brady, J. and Gibson, G. (1989) Visuallyguided, upwind turning behaviour of free-flying tsetse flies in odour-laden wind: a wind-tunnel study. Physiol. Entomol. 14, 3139.CrossRefGoogle Scholar
David, C. T., Kennedy, J. S., Ludlow, A. R., Perry, J. N. and Wall, C. (1982) A reappraisal of insect flight towards a distant, point source of windborne odor. J. Chem. Ecol. 9, 12071215.CrossRefGoogle Scholar
David, C. T., Kennedy, J. S. and Ludlow, A. R. (1983) Finding a sex pheromone source by gypsy moths released in the field. Nature, London 303, 804806.CrossRefGoogle Scholar
Elkinton, J. S., Schal, C., Ono, T. and Cardé, R. T. (1987) Pheromone puff trajectory and upwind flight of male gypsy moths in a forest. Physiol. Entomol. 12, 399406.CrossRefGoogle Scholar
Ford, J. (1970) The geographical distribution of Glossina. The African Trypanosomiases (Edited by Mulligan, H. W.), pp. 274297. Allen and Unwin, London.Google Scholar
Gibson, G. and Brady, J. (1985) ‘Anemotactic’ flight paths of tsetse flies in relation to host odour: a preliminary video study in nature of the response to loss of odour. Physiol. Entomol. 10, 395406.CrossRefGoogle Scholar
Gibson, G. and Brady, J. (1988) Flight behaviour of tsetse flies in host odour plumes: the initial response to leaving or entering odour. Physiol. Entomol. 13, 2942.CrossRefGoogle Scholar
Gibson, G., Packer, M. J., Steullet, P., and Brady, J. (1989) Host odour concentration effects on the orientation of tsetse flies to wind. Physiol. Entomol. 15, (in press).Google Scholar
Hargrove, J. W. and Vale, G. A. (1978) The effect of host odour concentration on catches of tsetse flies (Glossinidae) and other Diptera in the field. Bull, entomol. Res. 68, 607612.Google Scholar
Torr, S. J. (1988a) The flight and landing of tsetse (Glossina) in response to components of host odour in the field. Physiol. Entomol. 13, 453465.CrossRefGoogle Scholar
Torr, S.J. (1988b) Behaviourof tsetse tties (Glossina) in host odour plumes in the field. Physiol. Entomol. 13, 467478.CrossRefGoogle Scholar
Torr, S. J. (1989) The host-orientated behaviour of tsetse flies (Glossina): the interaction of visual and olfactory stimuli. Physiol. Entomol. 14, 325340.CrossRefGoogle Scholar
Turner, D. A. and Invest, J. F. (1973) Laboratory analysis of vision in tsetse flies (Diptera, Glossinidae). Bull, entomol. Res. 62, 343357.Google Scholar
Vale, G. A. (1974) The responses of tsetse flies (Diptera, Glossinidae) to mobile and stationary baits. Bull, entomol. Res. 64, 545588.Google Scholar
Vale, G. A. (1977) The flight of tsetse flies (Diptera: Glossinidae) to and from a stationary ox. Bull, entomol. Res. 67, 297303.Google Scholar
Vale, G. A. (1980) Flight as a factor in the hostfinding behaviour of tsetse flies (Diptera: Glossinidae). Bull, entomol. Res. 70, 299307.Google Scholar
Vale, G. A. (1983) The effects of odours, wind direction and wind speed on the distribution of Glossina (Diptera: Glossinidae) and other insects near stationary targets. Bull, entomol. Res. 73, 5364.Google Scholar
Vale, G. A. (1984) The responses of Glossina (Glossinidae) and other Diptera to odour plumes in the field. Bull, entomol. Res. 74, 143152.Google Scholar
Warnes, M. L. (1990) The effect of host odour and carbon dioxide on the flight of tsetse flies (Glossina spp.) in the laboratory. J. Insect Physiol. 36, 607611.CrossRefGoogle Scholar