ENEMIES OF THE FLY 53 



examined, and the stomachs searched for the wings of 

 Glossina, easily recognizable by their peculiar venation, 

 but none were ever found to have swallowed Olossina. 

 Twenty more birds were shot on Bugalla with similar 

 results. 



A common green tree frog was examined, and in fifty- 

 three cases no Glossinae were found in the stomachs. This 

 species spends the day among the vegetation on the 

 shore, but I think only feeds at night, so that it is not 

 likely to meet with Glossina. 



A large Agamid lizard haunts trees, around which there 

 is a certain space of open ground, and I shot five of them, 

 but their stomachs were found to contain only ants. 



It does not seem probable, in view of the above evidence, 

 that vertebrates play a great part in keeping down the 

 numbers of the adult fly. 



Of invertebrate enemies of the fly there is no doubt 

 that species of Bembex, sand-wasps or Fossors, are of 

 some value, but their distribution is very local. 



A full account of these most fascinating insects will 

 be found in the chapter on Hymenoptera : it suffices to 

 say here that two species ^ have been seen to store up 

 Glossina in their underground burrows, and that they seem 

 to know that fat full-fed flies, which they prefer for the 

 food of their larvae, are to be obtained from man and 

 other animals. I have seen the same in the case of a 

 species (unidentified) which preys upon Glossina morsitans : 

 as one walked along, pursued and harassed by the Tse- 

 tse, the Bembex would accompany one, flying round and 

 round searching for a fat fly. 



A species of Dragon fly (Cacergates leucosticta) which 

 is very common on the lake shore has discovered the 

 same thing, and individuals have several times been seen 

 to chase Glossina, and once or twice I have actually seen 

 them catch and devour the fly. On one occasion I was 



* B. forcipala, B. capensis. 



