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concentrate the attack on the periphery of the fly area (without disturbing the conditions farther in) and to do this only where it is possible to arrange for the settlement of the country treated. In this way the settlers themselves can be utilized for maintaining those conditions that render the country unsuitable for the existence of the fly, and it should thus be possible to keep the cost within reasonable limits. The area dealt with can then be extended as the occasion arises, and it might be thus possible gradually to reclaim permanently such land as is actually needed.

From what we can learn, the Ntambanana Settlement would appear to offer exceptionally favourable opportunities for an experimental attack of this kind. The settlers are already on the spot and would, no doubt, be willing to co-operate in the task of rendering their own land safe for cattle, if only they can be shown what to do and how to do it, and if, above all, they are properly organized for the purpose.

Seeing that the control of nagana is primarily a veterinary matter, it would certainly increase the chances of success if the Veterinary and Entomological Divisions were to combine forces in organizing and directing this experimental attack upon the fly. The details would have to be elaborated by the senior officers of the two departments, but the general lines of work suggested are the discovery and elimination of all tsetse breeding-places within the selected area; the construc- tion of artificial breeding-places (subject to arrangements for inspection at short intervals, and for the destruction of pupæ found); the destruction of thickets, which are essential for the fly, both by direct clearing and by simultaneous late burning of the grass; organized trapping and catching of the insects over an extended period, with an increasing scale of rewards as the insects become scarcer; and the laboratory breeding on a large scale of Syntomosphyrum glossina and other suitable parasites, for release within the fly area. No doubt, as the work proceeds, other useful measures will suggest themselves.

Annexure to No. 59,

SUGGESTIONS FOR TSETSE WORK IN ZULULAND.

Memorandum by Mr. R. H. Harris.

THE main work which has not yet been touched in Zululand is practical field experiments in the control of, the tsetse fly, and the settlers, who have all lost very heavily in cattle, and are still losing, are naturally looking eagerly for relief of

some sort.

t

This work embraces two problems, the first of which appears to be the more pressing to the present settlers; while the second is essential to the further opening up of country suitable for settlement.

ท

1. (a) Dealing with the first problem it would appear to be very important to ascertain, in view of the many seasonal sporadic outbreaks of nagana on occupied farms, whether the fly is actually permanent in the Settlement of Ntambanana or whether these outbreaks are due to other causes, such as a higher percentage of infected flies at certain seasons due to the temperature conditions, &c.

(b). If the fly is found not to be permanent, then it appears to be necessary to attempt to discover how it is introduced.

The

(c). If the fly is found to be permanent and breeding throughout the year in the occupied area, it would be necessary to conduct clearing experiments, &c. difficulty in doing this would be the question as to who should bear the expense. If borne by the Government, the difficulty arises of preferential treatment, for the Government obviously could not undertake to clear all farms.

2. (a) The second problem could be investigated on Crown land near the Tsetse-fly Station by selecting an area of, say, 500 acres in which fly is known to be present. It could be fenced off, and in one half all thickets and undergrowth could be cleared, and then by means of bait animals or dummies both halves could be tested over a period of not less than 12 months. At the same time various trapping and other devices could be tested as well as the driving out from the fenced area of wild animals likely to carry fly to and fro. All captured flies could be examined for infection by dissection, and the percentage noted. The most important period for catching and trapping would seem to be the dry season, when the periods of gestation and pupation are doubled-a maximum of 75-84 days being taken between

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generations in the dry season. The impression gained is that thickets are very essential to G. pallidipes, and valuable results are anticipated from the clearing of these, in conjunction with other methods such as catching, trapping, and burning. The main object of the experiments would be to discover what are the inimical conditions which can most effectually and economically be employed against the pest. Improvements and modifications would develop as the work progressed. It would be necessary also to continue laboratory work, especially in regard to parasite infestation, though to all appearances the natural parasites of G. pallidipes are not of much account, having possibly long ago struck a balance. The most promising parasite seems to be Syntomosphyrum glossinee, Wtstn., which has been carried through nine generations in tsetse puparia in the laboratory, and is very hardy and long-lived.

The main difficulty in making suggestions for a programme is a financial one, though possibly money will be forthcoming if it is desired that the work should be pushed to practical results. It would at present be impossible to give any accurate estimate of the cost of these suggested experiments, but every endeavour would be made to curtail expenditure.

24556

No. 60.

GOLD COAST.

THE ACTING GOVERNOR to THE SECRETARY OF STATE. (Received 23rd May, 1924.)

(No. 359.)

[Answered by No. 63.]

SIR,

Government House, Accra, 1st May, 1924. IN continuation of Mr. Philbrick's despatch No. 638 of the 20th August, 1923,* on the subject of tsetse fly investigations, I now have the honour to transmit, for your information, the accompanying copy of a report by Dr. W. A. Young, Acting Director of Medical Research Institute, on a visit made by him to tsetse fly areas in the Colony and Ashanti.

2. A copy of a memorandum on the subject by the Director of Medical and Sanitary Services is also enclosed. I agree with the views expressed by Dr. O'Dea in paragraph 7 thereof.

I have, &c.,

J. C. MAXWELL,

Acting Governor.

Enclosure 1 in No. 60.

REPORT OF A BRIEF VISIT made to a tsetse AREA TO OBTAIN SOME IDEA AS TO THE SETTING UP OF A CAMP TO INVESTIGATE TSETSE FLIES AS HAS RECENTLY BEEN DONE IN NIGERIA.

INTRODUCTION.

WHEN One looks at a spot map (see Xt) of tsetse flies for the Gold Coast, one is given the impression that to go into the bush anywhere would mean being continuously bitten by tsetse flies and so probably infected by trypanosomes.

The spot maps are quite correct, but the impression conveyed by them is entirely wrong, which means that spot-maps at present merely indicate that at some time or other a tsetse fly has been caught within a particular district. They give no idea whatever as to the intensity of "fly" nor to the time of year nor weather conditions, two important factors.

It would seem advisable, therefore, that a spot map, to be of real use, should have stated on it the month of the year, (2) whether tornado, rainy, or dry season, (3) some device for indicating intensity. The latter might be done by indicating by circles-the number of flies the observer caught per hour at the spot. For example, the usual signs used would merely indicate that tsetse had been found. One circle

Not reproduced.

* No. 56.

885/26

PUBLIC RECORD OFFICE, LONDON ALLY WITHOUT PERMISSION OF THE ¦ BE REPRODUCED PHOTOGRAPHIC-