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Distribution of tsetse flies.-There are few parts of the Province where some species of Glossina may not be found. The only part of the country which may be said to be fly free is Banda town, and the neighbourhood within a radius of about four miles from the town. During a residence of five days at Banda in September at the height of the rains, not a single Glossina was seen. This is probably due to the fact that the country has been extensively farmed for years. The natives are able to rear cattle in the Banda District, which is another indication of its freedom from tsetse fly.
Glossina palpalis and G. tachinoides exist along the banks of the permanent streams in Banda, but do not appear to travel up the temporary streams during the rains, possibly because these run dry so rapidly after the cessation of the rains. owing to the slope of the land, that little vegetation is able to grow to give the required amount of shade. Tsetse fly were taken at the following places:-
Glossina palpalis.-Kintampo--may be taken any time along banks of streams --16th January, 1913, 13th February, 1913, 17th April, 1913, 11th June, 1913.
G. palpalis.-Dortoban, 18th August, 1913; Fiamah, 22nd August, 1913; Mansu, 25th October, 1913; Ampamah, 27th August, 1913; road between Anyimah and Krabonsu, 28th August, 1913; Krabonsu, 28th August, 1913; road between Krabonsu and Kintampo, 29th August, 1913; road between Kintampo and Zongo on Gambaga road, 3rd September, 1913; Zongo-Gambaga road,-3rd September, 1913; Bjere. 12th September, 1913; Volta River at Bangbey ferry, 19th September, 1913; Bwe village, 22nd September, 1913; road between Bwe and Jeima (Northern Terri- tories), 30th September, 1913; Kaka, 8th October, 1913; road between Kunshi and Chirembue, 10th October, 1913; Chirembue, 10th October, 1913; road between Abease and Trowhe, 13th October, 1913; Attabubu, 15th October, 1913; Nsumia (B. Krachi), 29th October, 1913; Amantin, 12th November, 1913; N'kwanta, 16th November, 1913.
G. pallicera.-Kintampo, 14th June, 1913, 23rd June, 1913, 9th July, 1913, *12th July, 1913; road between Anyimah and Krabonsu, 28th August, 1913.
G. tachinoides.-Volta River at Bangbey ferry, 19th September, 1913; Bwe village, 22nd September. 1913; road between Bwe and Jeima (Northern Terri- tories). 30th September, 1913: on banks of Pru (road between Abease and Trowhe), 13th October, 1913.
G. longipalpis. Kintampo, 20th March, 1913, 16th April, 1913, 15th July. 1913: Kukuma, 10th August, 1913; N'koranza, 13th August, 1913: Dortoban. 18th August. 1913; Fiamah, 22nd August, 1913; Amumah, 26th August, 1913; Ampamah, 27th August, 1913: road between Ampamah and Anyima, 28th August, 1913; Anyima, 28th August, 1913; road between Anyimah and Krabonsu, 28th August, 1913; Krabonsu, 28th August, 1913: road between Krabonsu and Kintampo, 29th August, 1913; road between Kintampo and Zongo (Gambaga road), 3rd September, 1913; Zongo, 3rd September, 1913; road between Zongo and Dawa, 4th September, 1913; Dawa, 4th September, 1913; road between Kintampo and Sorbile, 17th September, 1913; Jugbey (Northern Territories), 20th September, 1913; road between Jeima and Bampewa (Northern Territories), 1st October, 1913: Jeima (Northern Territories), 29th September, 1913; road between Kintampo and Kaka, 8th October, 1913; Kaka, 8th October, 1913; road between Kaka and Kunshi, 9th October. 1913; Kunshi, 9th October, 1913; road between Kunshi and Chirembue, 10th October, 1913; road between Abcase and Trowhe. 12th October, 1913: Trowhe, 12th October, 1913: road between Attabubu and Nyumuassi, 19th October, 1913; Nsumia (B. Krachi), 28th October, 1913.
G. longipalpis.-Road between Nsumia and Tadieso, 30th October, 1913; road between Nsumia and Preniase, 2nd November, 1913; road between Preniase and Basa, 3rd November, 1913; road between Droma and Fakosi, 19th November, 1913. Gi, nigrofusca.-Kintampo, 14th April, 1913, 16th June, 1913; road between Kintampo and Kaka, 8th October, 1913.
G. submorsitans.-Road between Charandra and Dawa, 4th September, 1913: road between Dawa and Porta, 5th September, 1913; Porta, 5th September, 1913. G. medicorum.-Road between Preniase and Basa, 3rd November, 1913, two males taken.
The places where G. palpalis has been taken are indicated by a blue circle on the accompanying map. That portion of road between Attabubu and Nsumia from Kokofo to Ntrubusa is singularly free from fly, and the same remark applies to the road between Droma and Kumfia, although large game is said to be inet with
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in both parts of the country. Kinghorn, in his report on trypanosomiasis in the Western Province states that the range of G. palpalis is much greater than that of any other species in that Province. This is not the case in the Northern Province, where G. longipalpis is the most universally distributed tsetse fly, owing, as has already been remarked, to the type of vegetation which covers most of the Northeru Province being suitable for those species requiring a moderate amount of shade.
The range of G. palpalis in the Northern Province is confined to the monsoon forest of the southern end, and to the forest which covers the banks of the permanent streams. During the rains, when many of the smaller streams are brimful, the range of G. palpalis is increased, but with the subsidence of these smaller streams the range contracts again. It is unlikely that the banks of these On the banks of the Black temporary streams are much used as breeding places.
Volta and the lower reaches of the Pru G. tachinoides was much more common than G. palpalis.
Conclusions.-The Northern Province of Ashanti seems to be much less heavily I have no statistics of infected with human trypanosomiasis than the Western. Wade's findings in his tours of the latter Province, but Kinghorn, in 1910, found 97 cases amongst 16,654 natives examined by him, giving an incidence more than three times greater than my finding for the Northern Province.
Human trypanosomiasis has been known to exist on the West Coast of Africa for at least one hundred years, and there is no tradition of its ever having assumed epidemic form as it has of recent years in Uganda. It is said to be endemic, and that it has not spread with the alarming rapidity of the disease on the east coast is ascribed to the fact that the native races have acquired a certain degree of immu- nity against the disease. Reasoning from the analogy of other tropical diseases caused by protozoa, it is difficult to believe that this immunity is hereditary-there is no hereditary immunity against malaria or yellow fever, the only immunity against these diseases is an acquired one. Is the supposed immunity to human trypanosomiasis due to the disease having been acquired in a mild form? This is also difficult of belief.
It seems more probable that the difference in the virulence of the disease on the two sides of the Continent is due to the difference in the conditions to which the vector is submitted.
Kinghorn and Yorke have shown the effects of reduced temperature in retard- ing the development of T. rhodesiense in G, morsitans. It is not unlikely that some condition in the bionomics of G. palpalis in West Africa is inimical to its being Bouet and so efficient a transmitter of T. gambiense, as it is on the east coast. Rouband were unable to transmit T. gambiense in Dahomey and Casamance by means of G. palpalis, yet the Royal Society's Commission and Kleine had no diffi- culty in Uganda and German East Africa with the same trypanosome and fly. Rouband (Bull. Tropical Diseases, Volume I., No. 9) considers that the receptivity of a given species of Glossina for a given virus is not uniform throughout the extent of that species' distribution. He does not. think that climatic factors have a direct influence on the evolution of trypanosomes in the fly, because certain species, where several species of tsetse exist, are favourable to a virus while others are not.
Apart from these considerations, however, if one may judge from the ease with which pupa of G. palpalis are collected on the shores and islands of Victoria Nyanza, and the numbers of flies caught for laboratory purposes in a short space of time, G. palpalis must be much more numerous around that lake than it is in any Colony of West Africa (indeed, but little seems to be known about the breeding places of this whole genus in West Africa, and this is not because they have not been looked for). Again, big game, which acts as a reservoir, is more plentiful on the east side than upon the west, so that more rapid spread of the disease is to be looked for.
An interesting paper by Fiske (Bull. Entomolg. Research, Volume IV., Part 2, rage 95), upon the bionomics of Glossina, makes the suggestion that the females migrate periodically from more favourable to less favourable breeding grounds, that this is instinctively done to prevent overcrowding and for the purpose of maintaining the race in less favourable surroundings. He concludes that localities where males predominate are favourable, and where females predominate are unfavourable, to increase.
My experience of stations in West Africa, though not large, leads me to believe that females are more commonly caught than males. In Kintampo the Proportion is two females to one male. The total number taken, 261, is, however, too small to warrant any conclusion being drawn.
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