Published online by Cambridge University Press: 10 July 2009
Newly Hatched Tsetse (0–1 day old).
1. Neither species is affected by daily maximum temperatures of 95–102°F.
2. Possibly the death of any weakly tsetse is accelerated by a temperature of 102·5°F.
3. The critical zone for G. tachinoides is 103° to 105°F., but at the latter temperature 100 per cent. mortality is only assured if this maximum lasts for about 100 minutes.
4. The critical zone for G. submorsitans is 103·5° to 106°F.
5. If maintained for 60 minutes, 106°F. assures 100 per cent. mortality among young flies of both species.
Old Tsetse (over 10 days old).
6. The critical zone for G. tachinoides is 102° to 105·5°F.
7. The critical zone for G. submorsitans is 102·5° to 106°F.
8. The sudden increase in mortality among tsetse upon very hot days would appear to be directly due to the maximum temperature having entered the critical zone, and not to excessively low humidity or very high evaporation.
9. The critical zone for old flies starts at about 1°F. lower than for newly hatched flies.
10. G. tachinoides is rather more susceptible to high maximum temperatures than is G. submorsitans ; results also suggest that G. tachinoides cannot withstand an exposure of long duration at high temperatures as well as G. submorsitans.