220 JAS. J. SIMPSON—ENTOMOLOGICAL 
VIII. Bronomics oF GLOSSINA. 
In the Colony of the Gambia, only two species of Glossina, namely, palpalis 
and morsitans were observed by the author, and the chief points of bionomic 
importance have been given in more or less detail in the general narrative. It 
may be well, however, to recapitulate these. 
(a.) Glossina palpalis. 
Haunts.—W herever mangroves exist one is almost certain to find palpalis, but 
careful search failed to reveal either pupae or empty pupal cases. This is not 
surprising, as mud is the chief constituent in a mangrove swamp. At the time 
of my visit to the Colony, the river level was practically at its minimum, and 
consequently many small creeks were dried up, and areas which would be 
swamps during the dry season, were baked hard by the sua and much cracked. 
If, however, as is probable, the chief breeding period is during the rains, the breeding 
grounds must be removed some distance from the actual river basin, and the 
tsetse must follow the receding water, as they are seldom found in the regions 
which would correspond to the water-level during the rains. In addition to the 
mangrove area, however, there are scattered over the Colony numerous clusters 
of dense bush with abundant low undergrowth. The soil in these places 
consists of decaying humus, and is moist throughout the whole year, even in some 
places retaining a small amount of surface water. These places are always 
tsetse-haunts, and as there can be little doubt that they form centres for the 
dispersal of tsetses, it is to these that attention should first be directed when any 
clearing is contemplated. A good example of this is to be seen at Bakau and 
elsewhere at Cape St. Mary, a description of which has been given above. 
Abundance—In most places they attack singly, or at any rate, in very small 
numbers, but occasionally, in certain places, they literally swarm around, and it 
is with the greatest difficulty that one can avoid being bitten. Cases of this 
description were noted on the launch in the Bintang Creek, at Wassu and 
Tendaba; but this is not always an infallible sign of actual numerical excess 
over other places, being often due to other factors, ¢.g., movement. 
Movement,-—It is a matter of almost commonplace observation that tsetse are 
much more active and pertinaceous in their attacks on moving than on stationary 
objects, and for this reason, it seems fair to conclude that they rely more on 
their sense of sight, than on any other, in selecting their unwilling host. In a 
tsetse-haunt, if one remains absolutely motionless, in the majority of cases, not 
a single insect will be seen, but as soon as one begins to walk backwards and 
forwards, they at once dart out to attack. The same is to be observed in the 
case of horses and cattle. A similar condition of affairs holds good with regard 
to canoes; if these be anchored or tied up, one is comparatively immune from 
attack, but as soon as paddling is commenced, hordes of tsetse swarm around ; a 
good example of this was observed at Wassu (p. 202). Even more noteworthy 
