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assist us and was cheap in operation such as properly organized grass burning, the cutting off from the main bush of large and small sections, and the release of the parasites of the pupa-would be tested in such parts of the belt as were suitable to it. Further suggestions would arise in the course of the experiment and would themselves then be tested.

At the moment I favour two, alternative, areas—(a) the evacuated and largely isolated site of the recent sleeping sickness epidemic near Mwanza, and (b) the isolated Chinyanga fly-belt in the north of the Tabora district. In each district the present Senior Commissioner has shown the most active interest in the problem of the eradication of tsetse. In both areas are many open "mbugas," with cotton soil, the borders of which appear likely often to coincide with the fly's primary centres, and, if either should be pronounced to be fitted for special development as a cotton area, it will be most fortunate, for I regard it as important that, if possible, any area that is selected for our experiment should be capable of special and profitable development under the auspices of the Agricultural Department.

The Mwanza area has the advantages (a) that it is near the Lake and therefore more favourably situated with regard to water transport to a rail-head (Kisumu) for anything it may produce; (b) that it possesses an evacuated population which is probably anxious to get back, and can be re-settled as we desire and decide. But it is possible that it will be some time before it can be safely permitted to return. The Chinyanga area has the advantages (a) that it is only one day by car from the Central Railway at Tabora, (b) that there is an Administrative Station actually on the spot, and (c) that it is also particularly desirable to get rid of this area. which forms a dangerous link between any further cases in the Usukuma area and the great Brachystegia area infested by G. morsitans that covers most of the west of the territory. It may, however, be found, on closer investigation, that some other area will be preferable to either.

Cost. The cost of the examination will be defrayed from the sum I have already at my disposal. The probable cost of the experiment itself and the time that it will take, would emerge from my initial investigation, carried out in collaboration with the Veterinary, Administrative and Agricultural Departments, and I would then furnish an estimate. "I would regard no area as suitable in which very heavy special expenses would have to be incurred, as my whole object is to ascertain whether and demonstrate how tsetse may be eradicated cheaply, and, secondly, it would be my object to select an area, should there he one, the develop- ment of which will in itself be useful to the Territory, and calculated to return a profit on the expenses connected with it.

3. "Survey" Operations.

(i) In relation to the possibility of installing the policy described in the first section. A great deal could be learned in this connexion, and also in relation to the possibilities, local and general, of controlling tsetse, from a careful examination of the conditions obtaining along the margins of the cattle-keeping areas. I would like to have the opportunity of investigating here personally, in collaboration with the Veterinary Department and the local Administrative Officers.

(ii) I shall, during my next tour, traverse as much country, generally, as I have time for, in pursuance of my plan of revising the game preserves, and I shall do tsetse work as I go. If, while I am in areas which he regards as worth investiga- ting in relation to human trypanosomiasis, the Principal Medical Officer should be able to let a Medical Officer join me, it is possible that we might be able to collaborate usefully, and that work done thus conjointly will have greater value than work done by either of us alone.

(iii) General survey of tsetses.-Material for collecting, instructions and a request for assistance, were distributed to all districts for use by any officials travelling in the districts, and also to the appropriate Departments.

Some people have helped well, and the fact that, on the whole, the response has been disappointing, will, I hope, be remedied now.

4. Eland Domestication.

I consider that it is very important to attempt this. The eland promises to be an excellent draught and farming animal with good shape, great weight, good meat and some milk, and has done well where tried. It will hardly compete with cattle on their own ground, for their qualities are the result of long selection, but it should

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be an excellent substitute for cattle for the development of tsetse areas. old animals are relatively easily caught in numbers and tamed. It is a browser, so that, when farmed on a large scale, it should be an effective bush and tsetse reducer. I am particularly anxious to obtain all facilities for the capture of elands on a sufficient scale to admit of a thorough trial. They would be handed over to the Veterinary Department, whose willingness to co-operate in this connexion I have ascertained.

Cost. It was calculated that the cost of the initial drive and taming would not amount to more than £150, and probably not more than £100. Details that were obtained of methods successfully employed in German times for capturing elands and zebra for menageries showed that the former could be handled and tamed by a system of tethering, without the use of paddocks, and finally driven. This entails the employment for one month of a considerable number of natives, but it is likely that once the animals were handed to the Veterinary Department the latter would require to paddock them. Any requirements in this connexion would be dealt with by the Chief Veterinary Officer, but, for this, and for further consultation and arrangement with him, there is still time, as the first attempt to capture elands would not be made till May of next year.

Requirements.

Suitable Assistant.-I need very greatly and do not yet possess a good assistant from the point of view of research; and I would ask for one such assistant were it not for the present financial stringency and the fact that my Department's most pressing need for reinforcement, when it can be given, lies in another direction.

I would, however, like (if this should be regarded as useful) the training of new investigators who may from time to time be appointed to other Colonies, for the advantage that their assistance may be while they are with me; and, if any of these should be available shortly and the period for which they can stay should be fixed at an entire season, this will help to bridge the gap until I can be allowed an entomologist of my own.

I shall be away from my office during the greater part of my next tour and need greatly, also, and propose to ask for, a clerk, who would accompany me, and, assisting me in various important ways, relieve me of much hampering detail and enable me to increase my personal output of result by 50 per cent.

Summary.

The two main points on which of the conditions and possibilities existing along the margins of the cattle keeping areas with a view both to obtaining a large amount of useful and suggestive informa- tion and to inaugurating or preparing for the policy I have described in Section 1; and (2) the experiment in the eradication of tsetse from a belt of limited size, referred to in Section 2. In May, 1924 (May being the best month), an initial attempt to capture elands with the aid of the Wambugwe (of Arusha district) would (3) be made, if all can be arranged and the Chief Veterinary Officer is ready for them, and my remaining proposals (4) come under the heading of "Survey"; though some of this, if collaboration with a Medical Officer can be arranged, might be developed into useful local investigations in relation to human trypanosomiasis.

The cost of all investigations would be defrayed out of the sums already allowed me, an estimate will be submitted for the special experiment in the eradication of tsetse when the area has been selected and studied, it is possible that I next estimates ask for £100 in relation to the capture of the elands, and that the may in my Chief Veterinary Officer may need money for fencing in the same connexion, and, as regards personnel, I suggest that my need for a sufficiently qualified assistant in connexion with the tsetse work might be met for the time being by allowing me the training of new investigators destined for other parts of Africa. I propose, in addition, to ask for a special clerk.

would propose to work are (1) the examination

Pending the preliminary investigations I have referred to, it is impossible to say confidently that the policy and experiment I have suggested will be successful. But they seem most promising and it seems probable also that in no other way will it he possible, cheaply or on any large scale, to hasten the extermination of flies of the morsitans groun. It is certain, further, that even if we should have to modify it as we go along, the experiment will give us the most valuable information on the control of the fly, or alternatively, show us finally and usefully that such control

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is not, on a great scale, practicable. If, therefore, the preliminary investigations should show that no insuperable difficulties are present (a) of an administrative nature, (b) as regards cost, I hope very much that I may be allowed to attempt the experiment.

C. F. M. SWYNNERTON.

5. Grenville Place, S.W.5,

30th January, 1923.

885

SAB,

No. 49.

COLONIAL OFFICE to BRITISH SOUTH AFRICA COMPANY.

Downing Street, 2nd March, 1923. WITH reference to the letter from this Department of the 15th of January,* I am directed by the Duke of Devonshire to request you to inform your Directors that the report† forwarded with your letter of the 15th of December last‡ on the game destruction experiment between the Gwaai and Kana Rivers has now been considered by the Managing Committee of the Imperial Bureau of Entomology.

2. The views of the Committee are expressed in the enclosed memorandum. It will be seen from paragraph 6 that the Committee have formed the opinion that the evidence put forward does not satisfactorily demonstrate that game destruction alone offers an inexpensive and practicable method of controlling tsetse-flies over wide areas; and the Secretary of State feels sure that when the considered views of this expert body are such as the memorandum indicates, your Directors will recognize the importance of proceeding with the utmost caution in the matter.

3. As regards the question of financial assistance raised in the last paragraph of your letter under reference, the Secretary of State regrets that it is not practicable for a contribution to be made by His Majesty's Government towards the cost of the 'experiment.

'I am, &c.,

*Enclosure in No. 49.

C. T. DAVIS.

MEMORANDUM On the Report on the Game Destruction ExpeRIMENT IN SOUTHERN RHODESIA.

1. THE report of the Chief Entomologist. Southern Rhodesia, dated 20th October, 1922, with the covering Minute by the Director of Agriculture, dated 3rd November, 1922, on the experiment for the extermination of tsetse-fly by the destruction of game between the Gwaai River and Kana River, has been referred to the Managing Committee of the Imperial Bureau of Entomology.

The Committee, having considered these papers, desire to offer the following observations.

2. One of the most striking features of the report is the fact that, although game destruction has been in progress for three previous seasons, there was a marked increase of big game in certain portions of the area of operations in the fourth season, so that the number of animals shot in the fourth year was actually greater than in any preceding year. These facts sufficiently demonstrate that effective game destruction is a much more difficult and complex problem than its advocates would have us suppose, nor do the explanations for this irruption of game, advanced by Mr. R. W. Jack, in any way counteract this view.

3. That a reduction in its food supply would sooner or later cause a reduc- tion in the numbers of the fly itself might readily have been taken for granted without any expensive experiment, but the benefit secured will be temporary, unless the area dealt with is immediately placed under effective settlement; otherwise. the cost of game destruction may have to be borne indefinitely in order to check the periodical re-incursions of game that will take place. The actual eradication of the fly by this means is a very different matter, and there is no reason to suppose as a result of the present experiment that such eradication can be effected by this

means.

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4. From a scientific point of view the manner in which the evidence for the reduction of the fly is put forward is far from satisfactory. Mr. W. F. Fiske long ago pointed out that catches of flies at different places or at different times in the same place cannot yield any reliable evidence as to the relative density of the fly, unless the figures are presented in a standarized manner which he fully explained. Out of six sets of comparative figures, the Fiske formula had been used for one only, in the other cases there is nothing to show how long the catching lasted or how many collectors were working, with the result that the figures lose most of their value.

5. Again, another important and possibly vitiating factor has been ignored, namely, the meteorological conditions. It is well known that Glossinu morsitans is much less in evidence on dull than on sunny days, and wind also tends to make them less active. If, for example, the weather in one October was mainly hot and sunny, and that in the following October mainly windy and overcast, one would expect to get a reduction in the number of flies caught in the second October, even though the insects were really just as numerous.

6. It is difficult to see how any really useful or reliable conclusions can be arrived at by Mr. Jack's method of making a brief annual inspection of the experimental area for a fortnight in the month of October only. The unreliability of any deductions based on the comparison of catches on a single day at intervals of a year is sufficiently illustrated by Table 7 of the report; for, whereas Mr. Jack secured only two males at the Bira River (number of catchers and nets not stated), two days earlier Dr. Nobbs and Mr. de Buys without a net secured seventeen males and seventeen females at the same place. Table 7 alone suggests a progressive annual diminution of the fly; whereas Dr. Nobbs' experience indicates that such a conclusion may be quite erroneous.

Unfortunately, in the carrying out of these game destruction operations, the opportunity of securing scientific data that might have had some practical importance seems to have been lost. In the first place, a thorough survey should have been made of the distribution of the game and the fly before the destruction began, for without this no really sound deductions can be made as to the effects of the shooting. Further, such surveys should have been made periodically, especially in relation to the seasonal movements of both game and fly; and the influence of meteorological con- ditions and different types of vegetation on these movements should also have received attention. Although a passing reference is made to the effect of the great drought of 1921 on the game, its possible direct affect in reducing the numbers of the fly has been entirely ignored in considering the captures made in 1922.

In general, therefore, the Committee are of opinion that the evidence put fer- ward does not satisfactorily demonstrate that game destruction alone offers an inexpensive and practicable method of controlling tsetse flies over wide areas.

7. Apart from the foregoing considerations, the recent reports by Dr. H. L. Duke (see Proceedings of Royal Society, Series B. Volume 94, No. B. 660, 1st January, 1923), and Mr. C. F. M. Swynnerton (see Bulletin of Entomological Research, Vol. XIII, Part 3), on the epidemic of sleeping sickness in the Tanganyika Territory, both put forward very cogent arguments for the view that, in certain conditions. the destruction of game on a large scale may result in a serious danger to the health of the human population in the vicinity. In the circumstances the Committee venture to think that it would be unwise for any Government in Tronical Africa to adopt the policy of wholesale game destruction where there is any reason to suspect the existence of sleeping sickness.

8. In conclusion, the Committee desire to express their appreciation of the fact that those who were entrusted with the task of carrving out the experiment had to face many serious difficulties, often at some personal risk.

22332

No. 50.

REPORT ON THE COLLECTING OF INSECT PARASITES FOR NEW ZEALAND. A. FIELD WORK. The Common Earwig.

THE collecting of Earwigs, with the purpose of obtaining from them any insect parasites for New Zealand, began on 4th September last. And from that late until the end of November the work was continued almost daily.