In view of the statement recently made by A. Davidson that Glossina pallidipes Aust., can feed on the latex of Euphorbia tirucalli and Sarcostemnus viminale the authors discuss the digestive anatomy of the fly and describe experiments in Zululand designed to test this theory. Preliminary tests showed that the temperature of the surface of these plants was lower or only slightly higher than that of the surrounding atmosphere, whereas the temperature of the surface of a mammal is generally much higher. As tsetse-flies apparently do not probe a cool object unless acutely hungry, it was found necessary to warm the naturally cool surface of the plants used in the experiments. The results obtained show that the flies are incapable of piercing the plant tissues and, if given an opportunity to feed on latex as it occurs in nature, soon die without reproducing. Moreover, the latex had an undoubtedly toxic effect on those flies that were artificially induced to feed on it through a membrane.
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