202 JAS. J. SIMPSON—ENTOMOLOGICAL 
vegetation on the river bank was very dense and overhung the water. It 
consisted chiefly of palms, pandani, ferns, and thick bushy shrubs (fig. 8). No 
Fig. 8.—View on the River Gambia beyond Barijali showing the dense nature of the 
vegetation which consists of Ferns, Palms, Pandani, &c., and is a typical palpalis- 
locality. 
sooner had we pushed off from the bank than numbers of biting flies assailed us, 
The following TABANIDAE kept hovering round, T'abanus secedens, T. fasciatus and 
T. taeniola, but as movement is very restricted in this type of canoe, none were 
actually caught. It was different, however, in the case of tsetse; these simply 
swarmed round and attacked persistently. After a number of specimens were 
secured, no further attempt at capture was made, and it was with difficulty that 
we managed to guard against too many bites. A ground-nut steamer was being 
loaded at Wassu, and here tsetse occurred in such numbers and so persistently 
darted from one person to another that a distinct humming sound was to be 
heard. After a very short stay, we pushed off and were followed by a large 
number of these insects, but by the time we had reached 70 to 80 yards from the 
bank, all had disappeared. On returning to camp at 1.30 p.m. we caught one 
Stomoxys nigra and one tsetse in the stable. 
The opposite bank of the river bore very little in the way of vegetation ; 
clusters of ferns and a few palms were scattered about. At 2 p.m., we crossed over 
to this side and moved slowly up-river to opposite Wassu, again keeping within 
50 yards of the bank the whole way. The only Tabanid caught was Tabanus 
taeniola, but tsetses were quite as troublesome as on the other bank; two were 
caught in coitu at 3.30 p.m. and must have flown from the bank, some 50 yards, 
in this attitude, as they were thus seen approaching the canoe some yards off. 
The identification of the tsetses, secured on these two canoe trips, was a matter 
of some difficulty. It was well-nigh impossible to assign them to any definite 
species on the basis of external characters alone. In some respects they resemble 
G, tachinoides, e.g. in their small size and in the extent of the pale markings on 
