29 



laboratory. The parasites do not as a rule become active until the 

 afternoon, remaining hidden until that time beneath objects on the top 

 of the ground, or buried beneath the surface of the soil. A Bombyliid 

 fly, Thyridanthrax abruptus, Lw., parasitic on G. morsitans in Rhodesia, 

 was also reared from pupae. This fly is not uncommon in the fly area. 

 Two Chalcids, Stomatoceras micans, Wtrst., and an apterous species 

 [Eupelminus tarsatus, Wtrst.] were bred from the pupae. About 

 1 per cent, of the Mutillids showed evidence of a Chalcid hyperparasite. 

 No parasites have as yet been reared from pupae from the proclaimed 

 area, a fact which may explain the numerical superiority of G. morsitans 

 in this region. 



Observations on the larva of G. morsitans showed that the slimv 

 secretion which covers it when newly born, is protective against such 

 ants as occur in breeding places and probably keeps the cuticle from 

 being injured when the larva burrows into the soil. The condition of the 

 soil is an important factor in determining the breeding place. In 

 nearly every case, breeding places were found beneath a fallen and 

 decaying tree, w^hich had been prevented by its branches from touchino- 

 the ground and which kept an area beneath it shaded and free from 

 moisture. Few pupae were found in hard clayey soil beneath trees. 

 Pupae may be deposited in cavities of dead trees, in which a certain 

 amount of soil has collected. The chemical composition of the soil 

 is immaterial, so long as it is friable, nor is the orientation of the breed- 

 ing place important, provided the pupae are sheltered from the direct 

 rays of the sun. In Nyasaland, the favourite situations are near game 

 and native paths or near water-holes. 



On his return to the proclaimed area in June, the author found an 

 abundance of flies along the road running west from Domira Bav 

 where clearing operations had been carried out in the previous January. 

 This was due to the fact that many trees had fallen before being com- 

 pletely severed, a condition which formed an ideal breeding place for 

 the fly.* Many pupae were found on a part of the area from which the 

 fly had temporarily receded, on account of drought. These may 

 repopulate the area when a change of conditions takes place. 



Experiments in liberating marked flies confirmed the supposition 

 that, in passing from a morsitans area to a free area, the same flies 

 which had been hovering round continue to follow for a considerable 

 distance. Motor cyclists coming into Fort Johnston have asserted 

 that the flies settle on their backs and are carried into the township. 

 The increased motor traffic may be indirectly responsible for the high 

 mortality of cattle from trypanosomiasis which has occurred during 

 the past few months at this place. 



The sense of sight and of smell probably play a part in attracting 

 flies to moving objects, but this statement requires further confirmation. 



Glossina hrevipalpis was found in February in a limited area of the 

 Lingadzi estate, eight miles from Lake Nyasa. The fruit trees growing 

 on the spot were bananas, mangoes and citrus trees ; three indigenous 



*[Tliis observation is of no little imjjortance, for it serves to indicate 

 that if clearing operations are carried out carelessly they may actually 

 cause an increase, instead of a diminution, in the numbers of the fly. 

 In this instance, it seems probable that the mere clearing of all under- 

 growth, without felling the timber, would have been both jnore effective 

 and more economical. — Ed.] 



