+ o THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
V. TRANSMISSION EXPERIMENTS 
A tsetse fly, Glossina palp alls ^ is practically ubiquitous in the Gambia. It is particu- 
larly numerous among the mangrove swamps, and for this reason it is locally called a 
mangrove fly. It is, however, seen all along the river, far above the brackish water in 
which the mangroves grow. Though the flies, as a rule, seem to prefer the immediate 
neighbourhood of some large expanse of water, they have been seen and caught in the 
bush at some distance (two miles) from any collection of water. We have taken 
specimens just outside Bathurst, everywhere through British Kommbo, and at many 
places along the river as far as Sunkunda. They were seen at Walia, and everywhere 
on the river itself they were a most pertinacious and disagreeable pest.* 
It was with this fly naturally that we made our first attempts to transmit 
trypanosomiasis from infected to healthy animals. 
We first allowed flies caught in British Kommbo, where there was a good 
deal of equine trypanosomiasis, to feed upon healthy rats. Our results were alwavs 
negative. 
A detailed account of these experiments follows : — 
Experiment i. — A white rat was selected, and tsetse flies caught in the bush 
near Bakau were fed upon it in the following manner and cn the following dates : — 
Sept. 1 4, 1 902 — 4 flies out of a batch of 6 fed. 
3 >> It 55 
4 of the flies caught on the fourteenth also fed. 
a batch of 6 fed. 
3 flies caught on previous dates fed. 
a batch of 4 fed. 
1 flies caught on previous dates fed. 
4 flies out of a batch of 1 7 fed. 
3 freshly caught flies fed. 
3 55 55 55 
O 
° 55 55 55 
Altogether, 44 flies {Glossina pa/pa/is) caught from the bush at Oyster Creek, 
about three and a half miles from Bathurst, were fed on this rat at periods varying from 
*In spite of a careful search, we never succeeded in finding G!o:sina in Senegal. No tsetse flies were seen in the 
mangrove swamps in the neighbourhood of St. Louis, which, in the Gambia, would certainly have sheltered myriads of them. 
Traders and residents in St. Louis and Dakar failed to recognize the specimens of Glossina which were shewn to them, 
and officers on steamers plying on the river Senegal, between St. Louis and Kayes, had never seen the fly. We were, however, 
told that it occurred to the South, on the River Kaolakh. 
The absence of Glossina from a district in which we failed to find equine trypanosomiasis forms, perhaps, a striking 
coincidence. 
5' 
T 5 
55 
15 
1 1 
16 
55 
17 
, •> 
18 
'5 
T 9 
55 
2 3 
55 
24 
Oct. 
1 
3 
