SLEEPING SICKNESS 
95 
at rest, usually remains on the earth hidden from view by the leaves of any low-growing 
form of vegetation or by fallen leaves, while Bagshawe, in Uganda, has shown that dry earth 
is necessary for pupation. The tly appears to object to wind almost as much as to direct 
sunlight. To determine its presence in any locality it is necessary to sit down quietly in the 
deepest shade available and in a sheltered spot near the margin of the open water of a 
stream or pool, and to wait there patiently for at least half-an-hour before one can say with 
any degree of certainty that it is absent. The fly is difficult to catch and is most easily 
taken with a net when settling on the body of a native. To one with sufficient experience 
it can be identified, without actually catching a specimen, by the peculiar buzzing noise it 
makes when flying, and by the quick darting way in which it flits from place to place. 
(r. palpalis is never very persistent in its attempts to obtain blood and will disappear after a 
few unsuccessful attempts have been made to capture it, thus differing very markedly from 
G. morsitans. The flies can be driven from shelter by disturbing scrub and fallen leaves 
with a long cane. When so disturbed they may attempt to settle and feed. They can, and 
often do, bite through clothing, but the latter, especially when of a white colour, certainly 
affords great protection. 
G. palpalis appears to feed in the dry season most freely between the hours of 8 a.m. 
and 11 a.m., and is not, as a rule, much in evidence after these hours. This is possibly due 
to the fact that, at this season, a strong wind sets in daily about 11 a.m. and continues 
blowing until late in the afternoon. In the rainy season, if the day is rainy or dull, the 
flies do not appear to feed at all. If such a day clears up in the afternoon they may 
become active. If, at this season, the day be fine with a bright, hot sun and little or no 
wind, the fly feeds as in the dry season, between 8 a.m. and 11 a.m. At any time of the 
year there is very little danger of being bitten after 5 p.m. G. palpidis is much more 
numerous during the rainy season. 
(ii) Of G. hioi-Kifant!. This species seems to feed most freely from immediately after 
sunrise until about 11 a.m., becoming troublesome again about 4 p.m., and continuing to 
annoy both man and beast until the last ray of light has died out of the sky. It is 
exceedingly greedy of blood, and appears, when feeding, to be quite indifferent to the 
chances of destruction. It is often seen in large numbers, miles distant from the nearest 
stream or pool, but at the same time is extremely numerous near rivers. The latter fact 
probably depends on the presence of big game which attracts the flies to these localities. 
G. morsitans bites freely in dull and rainy weather, and is most numerous after the first 
rains of the season have set in. 
3. Food siippli/ of G. jHilpalis. Captain Ensor notes that, in the southern part of the 
Bahr-El-Ghazal Province, the rivers are not sufficiently large to harbour many crocodiles 
and hippopotami. In this region, apart from man and big game, aquatic birds probably 
furnish it with its meals of blood. 
4. Conditions inflnencimj the range of G. palpalis. Apart from what has been already 
stated. Captain Ensor mentions an interesting observation to the effect that the two species 
of Glossina ajppear to possess what he terms “definite spheres of influence” and never 
encroach upon each other’s huuting grounds. He adduces evidence in confirmation of this 
statement, and says that, in their enthusiasm for blood-sucking, flies of the G. morsitans 
species will often follow one into a palpalis area, but that then they almost invariably 
disappear in a minute or two, their place being taken by hungry specimens of G. palpalis. 
The normal range of the latter in the absence of G. morsitans he places at probably not 
more than ten or twenty yards from the open water which they haunt. He further states 
that solitary specimens of G. palpalis are sometimes met with in houses situated long 
Glossina 
palpalis 
Glossina 
morsitans 
