TRYPANOSOMIASIS EXPEDITION TO THE CONGO 53 
in length and 4-5 mm. in width. The anterior end is roughly conical, the posterior 
is rounded. All the external structures seen in the larva can he made out on the 
external surface ot the puparium. The cuticle shows annular ridges. 
The duration of the puparial stage is from a fortnight to three weeks. 
During our stay at Wathen, Mr. Bentley showed us, among his collection of 
insects, a large light-brown fly which he believed to be developed from the floor 
maggots. Specimens caught in the boys' dormitory at the Wathen Mission were soon 
after brought in by one ot our collectors, and later, while searching a native hut infested 
with 'floor maggots,' we saw one of these flies resting on the grass wall. Many 
others were subsequently found in the same building, sitting motionless amongst the 
beams and cob-webs of walls and root. Because ot their colour, which corresponded 
exactly with the smoke -stained straw and ratters of the huts, they were difficult to 
see, and in the dark interiors more difficult to catch. 
This fly, seldom one of any other species, has since been found in many huts 
infested with maggots. We were told that the fly deposited its eggs on the ground of a 
hut, particularly in spots where urine had been voided. As a rule the fly is silent, but 
on one occasion we observed it buzzing loudly, fly in at the door and go directly 
beneath some bed mats which were raised by a low platform, some eight centimetres 
from the floor. 
Both Mr. Bentley and the natives state that this fly never bites men. 
The native name at Wathen for all flies is ' Nwanzi ' or ' Mbwanzi.' The name 
for the fly which we describe is ' Nkulu Mwanzi.' The fly is thick set, and is of about 
the size and build of a 'blue bottle.' It is about 10-12 mm. in length, and once seen 
can be easily recognized. Its general colouring is tawny, but the small black hairs 
covering its body give it a smoky appearance. The head is large, as broad as the 
thorax, and protrudes in front ot the eyes, which are when fresh a reddish brown in 
colour. The eyes are separated from each other, below, by a considerable interval and 
appear small in comparison with the size of the head. The proboscis is folded beneath, 
the head in a deep groove, and is inconspicuous while in this position. 
The palpi are club-shaped and covered, more particularly at their apices, with 
conspicuous black bristles. The third joint ot the antenna is long, yellow, flattened 
from side to side, and rounded at its apex. It bears an arista which, thickened at 
its base (probably jointed), tapers to a fine point. The arista bears fine black hairs 
along its upper and lower borders ; long at its base, the hairs become short and 
slanting at its apex. The dorsum of the thorax is flattened, and marked by 
longitudinal black and brown stripes, the transverse suture is well marked. The 
thorax is covered with fine black hairs and studded with rows of black bristles, which 
are particularly long on the sides. The squamae are very large, vellow in colour, 
and completely cover the yellowish-white halteres. The abdomen apparently consists 
of five segments. Jt is covered with long black hairs, and bears a few long bristles 
