190 JAS. J. SIMPSON—ENTOMOLOGICAL 
It is thus seen that the mangrove area corresponds, at any rate in the Gambia, 
with the extent to which the tidal influence is felt in the dry season, The nature 
of the vegetation behind the bank-fringe varies but little in the whole course of 
the river, except perhaps in the Niumi Province (the most westerly on the 
North bank), where there is a dense forest of small trees of no great extent. 
The river is studded, especially in its middle portion, with islands of various 
sizes. The chief of these are :—Fort James, Elephant, Pappa, Pasul, Pasali, 
Ba Faraba, Baboon, Kai-ai and MacCarthy Islands. None of these, however, 
are inhabited, except MacCarthy Island, which will be referred to later. With 
the exception of Fort James Island, which is merely a large rock in the middle 
of the river, and which was formerly used as a fortress, they are all densely 
covered with vegetation which partakes of the character of that on the 
corresponding part of the river banks, and are literally swarming with flies, 
which make a fierce attack on the occupants of passing craft. 
Having thus considered the types of vegetation which fringe the river banks, 
let us now proceed to an analysis of the diferent plant associations in what may 
be termed the interior. Only in one part, namely, the Niumi Province in the 
north-west, is there anything approaching a tropical forest. This consists of 
trees of vastly different sizes, with a dense undergrowth of small scrub, bound 
together by epiphytes of various kinds. In places, however, and especially 
towards the edge, the large trees disappear and are replaced by smaller forms of 
a more uniform size, while the ground is covered with grass interspersed with a 
few small shrubs. Epiphytes are almost entirely absent. 
Scattered throughout the whole Colony are fresh-water swamp forests of 
very limited extent ; they occur generally in long belts and vary considerably 
in formation. Some contain very large trees scattered amongst others of a 
smaller size, while the ground is covered with a matted net-work of shrubs. 
Figure 1 shows a path cut through a belt of this type. In others the large 
Fig. 1.—Path leading to well near|Bakau Village. A fresh-water swamp forest in which 
G. palpalis are abundant, 
