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42
It could not be studied as thoroughly as was desired. Conversely, the fly may benefit to a proportionate extent on islands where the breeding grounds are very restricted in extent, for it cannot get far away from them, no matter how extensive its food- hunting flights may be in point of time. Its hosts are often abnormally numerous; or they may be abnormally scarce, on islands. Its natural enemies may be absent, or unusually numerous. Finally its competitors, in the form of Tabanids and other biting flies, may affect its general welfare in more ways than were guessed until the very end of the period covered by this report, and many species common to the main- The environ- land are absent-or, at all events, have not been seen on the islands.* ment supplied by the islands is, in fact, abnormal, and its effects on the fly have corresponded. This circumstance has aided the course of the investigations in innumerable ways, for each island,* as it stands, is in the nature of a completed experiment in clearing, partial exterminations of hosts, etc., of which it was only left to record the results. The choice of a site for the work is believed to have been well justified.
CONCLUSION TO PART I.
57. Before these investigations were begun a theory was advanced,† based on a review of the literature, as to the manner in which an equilibrium between Glossina palpalis and its host might be maintained. This was taken as the working hypothesis, but it was quickly overthrown.
For nearly a year no satisfactory substitute could be found which took-as any such theory must take all observed facts in Glossina bionomics into account, and which comported with all. That outlined in the preceding pages was suggested in September, 1914, and seemed to meet all the exacting conditions.
58. It seemed at first not merely unlikely, but unreasonable, to assume that numerical abundance and rate of reproduction should be controlled by nothing more tangible than a gesture of annoyance on the part of a grazing antelope. None the less, the whole structure of palpalis bionomics seemed to depend for its stability upon the truth of the assumption. During six months the new theory was put to numerous tests, and withstood them all very satisfactorily. It is believed that it may safely be used as a basis for consideration of the economic aspect of the problem presented by Glossina palpalis in Uganda.
59. In many, or most, essential points the new theory happily agrees with that is the same in both. Both first put forward. The rôle taken by "natural enemies
assumed that flies left a too favourable region before their numbers had increased to a point which would affect the welfare of their hosts. The first did not, the second does, explain how this could come about.
80. The principal discrepancy between the two is the character of the dis- persive movement. This was originally assumed to be limited to one sex, and the phenomenon of sex disparity was hypothetically explained by the dissociation of the sexes brought about in this manner. A wholly different explanation was found to apply, and Glossina proved to stand as an exception amongst most if not all free- living, biting flies, in that one sex (only) is freely attracted to its hosts, whether or not desirous of feeding. This fact was only once to the writer's knowledge hinted at in literature, and then in connexion with another species of Glossina than palpalis.§
• In this connexion it may be worth noting that as a parasite of reptiles it has few competitors. It undoubtedly does favour reptilian host over any mammalian known with the possible exception of the marsh buck.
"Bulletin of Entomological Research," September, 1919.
: A large amount of data accumulated in the course of the numerous experiments, "fly surveys,'
etc., much of which deserves presentation in detail as supporting evidence, proved to be so cumbersome that it was thought advisable to eliminate it altogether from this part of the report. It will be placed in different form and presented as a series of disconnected articles in
Part IV.
The fact is that, bionomically as well as structurally and physiologically, these many points of resemblance between Glossina and the true body parasite of vertebrate classed as "Pupipera," which serve equally to separate it from the free-living, biting flies, to which it bears superficial resemblance. It is really a body parasite with fairly definite host relations, and not to be classed with the Tabanids, mosquitoes, stomoxys, etc., which alternate between two wholly different sorts of food at different stages and resemble parasites only in the final.
35714
SIR,
(No. 491.)
43
No. 39.
NEWFOUNDLAND.
THE SECRETARY OF STATE to THE GOVERNOR. [Answered by No. 43.]
Downing Street, 23rd September, 1915. WITH reference to your despatch No. 70, of the 5th of April last, I have the honour to request you to inform your Ministers that the other Self-governing Dominions and the Australian States, with the exception of Tasmania, which has promised to contribute for one year only, have agreed to continue their subscrip- tions to the funds of the Imperial Bureau of Entomology for three years from 1916. 2. As the Bureau is supported by the Empire as a whole, your Ministers may wish to reconsider their decision not to contribute to the Bureau, even if they do not see their way to make more than a nominal contribution of, say, £5 or £10 a year.
I have, &c.,
44851
SIR,
No. 40. UGANDA.
A. BONAR LAW.
THE ACTING GOVERNOR to THE SECRETARY OF STATE. (Received 29th September, 1915.)
(No. 239.)
Government House, Uganda, 20th August, 1915. In continuation of my despatch No. 222, of the 30th July, 1915,† I have the honour to transmit the second portion of the report by Mr. Fiske on the result of his investigations on Lake Victoria.
2. Mr. Fiske is expected to arrive in Entebbe towards the end of August, prior to the commencement of further research work on the lake shores in the East Africa Protectorate, and further sections of his report will be forwarded in due course.
I have, &c.,
H. R. WALLIS,
Governor's Deputy.
Enclosure in No. 40.
ECONOMIC ASPECTS OF THE PROBLEM PRESENTED BY GLOSSIÑA PALPALIS IN UGANDA.
BY MR. W. F. FISKE.
PART II.
THE epidemic of sleeping sickness which decimated the population of the lake shore and islands in Uganda was checked by removing the survivors to the interior, out of contact with Glossina palpalis. The area thus depopulated, and still closed, includes all the islands, except a portion of one, and a belt, some three miles in width, the entire length of the coast line, interrupted at a few points where necessary ports of ingress have been established. But for these ports Uganda is shut off, as by a wall, from the advantages which its location upon the lake naturally afford it. The quarantined area could hardly be more inconveniently located and disposed.
2. Contrary to expectations when the lake shore and islands were depopu- lated, the flies have continued to be infective. A source of infection has been traced to certain species of antelope, on one of which at least (the marsh buck) the fly freely feeds. The disease has thus become endemic (it may always have been so), and in some parts of the closed area there is every reason to believe that the proportion of
• No. 15.
+ No. 38.