270 GLOSSINA PALPALIS [CH. 



hole in the side ; the contents had been devoured evidently by 

 parasitic insects, probably belonging to the Chalcididse. 



The adult fly possesses numerous enemies, none of which, 

 however, seem to be of very great importance in checking its 

 numbers. Doubtless numerous insectivorous birds and reptiles 

 must prey on the fly, but again precise information is lacking. 

 The gorged insects are often carried off by a large species 

 of wasp (Bembex), in order to furnish its burrows. Carpenter 

 found no less than 31 tsetse-flies in the burrow of a species of 

 Bembex occurring in Uganda. Roubaud often observed G. 

 palpalis captured by spiders of the genus Dolomedes, which live 

 on aquatic plants at the edge of streams and hunt both Diptera 

 and Neuroptera. Ants are said to be very dangerous enemies, 

 and when tsetse-flies are kept in cages they are frequently 

 attacked and destroyed by swarms of a very small species, 

 Pheidole megacephala F. The tiny ants seize hold of. the legs 

 and wings of the flies, which soon succumb to the attacks of 

 these redoubtable foes. 



It is possible that in nature various species of Cincindela, 

 the tiger-beetle, prey on the tsetse-fly, for they are common on 

 the banks of streams. 



G. PALPALIS and Disease. 



It is well known that in nature sleeping sickness (T. gambi- 

 ense) is mainly, if not entirely, transmitted by G. palpalis. 

 Although it may be possible to infect other species of tsetse- 

 flies in the laboratory, the distribution of sleeping sickness 

 coincides so closely with that of G. palpalis, that there can be 

 no doubt of its importance in the spread of the disease. 



In addition a number of the trypanosomiases of animals 

 have been shewn to be spread by this species. Thus it is the 

 " host of choice " for T. cazalboui, and moreover has been 

 proved capable of transmitting T. brucei, T. dimorphon, 

 T. pecaudi, T. nanum and T. pecorum. It is probable that 

 the trypanosome of crocodiles is also carried by G. palpalis. 



