Trap-catches, nutritional condition and the timing of activity of the tsetse fly Glossina longipennis (Diptera: Glossinidae)

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Abstract
Samples of Glossina longipennis Corti, taken over four days in traps (baited with acetone, cow urine and octenol) at half-hourly intervals during their restricted activity periods at dusk and dawn, were analysed for their nutritional condition. For both sexes, trap catches were highest at the end of dusk, between 19.00 and 19.30 h, associated with a significant increase in numbers with the low haematin content characteristic of flies estimated to have fed more than 60 hours previously. Also, the mean fat content of these flies was significantly lower than that of those trapped earlier. There was considerable day-to-day variation in the numbers of flies trapped, and in the numbers of low haematin and low fat flies. It is concluded that the nutritional condition of the fly probably influences the timing of the onset of activity, but possibly the fly's approach to the trap.