Field responses of tsetse flies (Diptera: Glossinidae) to odours of men, lactic acid and carbon dioxide

Abstract

The numbers of Glossina morsitans morsitans Westw. and G. pallidipes Aust. attracted to odour at a distance were studied by catches in Zimbabwe-Rhodesia from an electrocuting net near a stationary odour source. Also, the numbers of flies attracted to an ox and the proportion of flies engorging on it when it was sprayed with L-lactic acid were assessed from the numbers of fed and unfed flies caught by a pair of nets around the penned bait. The body odour of men depressed by up to four-fifths the numbers attracted to ox odour from a distance. Lactic acid, which was shown to occur on human skin, produced a similar effect, and when sprayed on an ox it reduced by about half the proportion of attracted flies that engorged. Human breath was mildly attractive, due largely or entirely to its content of carbon dioxide.