58 NATURAL HISTORY OF GLOSSINA PALPALIS 



When a tree is torn up by the wind and, unable to 

 fall, is held up by its neighbours, the roots and earth 

 embraced by them form an ideal shelter for pupae if the 

 tree is near enough to water. One such was found on 

 Kimmi in 1918-19 and is here illustrated. In the loose 

 dry earth forming an area of a few feet square under the 

 roots, four boys in half an hour secured 309 pupae, giving 

 a rate of 154-5 per boy-hour, which is extremely high. 

 Search was made for pupae in other localities near this 

 tree, but the result was only 28 per boy-hour ! 



Lastly, thick bushes, especially the " Oluzibaziba " 

 (Alchornea), provide shade all the year round, and if the 

 soil and other conditions are suitable, pupae may always 

 be looked for there with success. 



The illustration shows a very favourite collecting ground 

 on the fly beach of Damba Island : under the bushes 

 close by but out of reach of the water. 



Variable shade is formed by low undergrowth or creepers 

 or dense young growth of bushes near the ground. I 

 have been much struck with repeated evidence of the fly's 

 care in selecting spots where new young growth is rapidly 

 forming dense shade, and the quickness with which such 

 shelter is seized upon by the mother as suitable. 



It was a common occurrence to find a cluster of some 

 creeper forming a dense tangle of fresh green that provided 

 admirable shade for the pupae, and investigation of the 

 pupae found there showed that they were in a very early 

 stage of development ; that is to say, had been recently 

 placed there. On Wema a very thick tangle of young 

 sprouts of a species of Polygonaceae was found on a ridge 

 of sand, projecting so as to arch over the surface below : 

 one boy found here eighty-eight pupae, of which 91 per 

 cent, had only recently been deposited, for they were 

 in a very early stage of development. 



Moreover, only six empty cases were found from which 

 the adult fly had emerged. These facts show that the 



