CO885-(18-19) — Page 12

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C.O.885

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and 2 females had the left mid-leg dêficient, i.e., 1 fly had wandered 900 yards from its original place of capture, and 4 flies had wandered 300 yards from their original place of capture.

The flies identified as marked on other days were noted and killed.

Experiment No. III.-On the 16th I marked at the ford, by dividing the right of the mid pair of legs through the tibio-femoral joint, 65 flies (22 males and 43 females).

On the 17th, at H., 109 flies (43 males and 66 females) were similarly treated. In the afternoon I took these and the flies marked on the 16th to a spot above the Mpanga waterfall, estimated by Mr. Haldane and myself as certainly a mile from the ford. Here were released nominally 65 males and 199 females, but several had died.

The 18th was rainy and sunless.

On the 19th there were caught at the ford 429 flies (191 males and 238 females). Of these 2 males and 6 females wanted the right mid-leg, i.e., on the 3rd day 5 per cent, of the flies liberated a mile away had been recaught.

Experiment No. IV-A repetition of No. III.

On the 22nd 89 flies (37 måles and 52 females) were marked by the removal of the right hind-leg, taken to a spot above the fall and there released. A fly (female) caught during the operation had the right mid leg wanting. On the way back to camp I visited the river about half a mile lower down in the gorge where it is difficult of access. Here 7 flies were caught, one of which was a female I had released half an hour before.

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August 24th. Of 135 flies caught at the ford 1 male had the right mid-leg deficient.

August 26th. Of 199 flies caught 1 male and 1 female had the right mid-leg deficient, and 1 female had the right hind-leg deficient.

On September 2nd I visited Harubale from Kasunga. 163 flies were caught at the ford.

Two females had the right mid-leg missing, 1 had the right hind-leg missing. Thus, of the 174 flies released above the fall on August 17th, 14 (4 males and 10 females) had been retaken a mile below, and of the 89 released on the 23rd 2 females had been retaken a mile below (time had not been sufficient for the last experiment).

These figures, as far as they go, tend to show that females fly further than males, but they are, of course, too small for definite conclusion.

They show at any rate that flies will wander along a river such as the Mpanga

a mile.

The natives nearest the Mpanga fall are those of Harubale.

There was no question of flies following human beings, for to reach the village from the fall one is compelled to make a wide detour.

In the large number of flies I examined I noticed that a few had limbs missing, I was but in such a way that it was evident they were not flies marked by me. careful not to count these. In a few doubtful cases where I was inclined to discuss the matter with my "dresser," who always helped me, he would not admit of any doubt, and all such flies were rejected.

When I reached Bukarungu I carefully examined a series of 1,088 flies to

determine what proportion had lost limbs from casualty or disease.

I found that in one a fore-leg was gone; in six a mid-leg; in four a hind-leg. In every case but one the whole limb was absent, so that one required a lens to clearly make out the stump (in the remaining case the limb had been divided through the tibia).

One or more tarsi are of course often pulled off in manipulation.

In my experiments the whole of the femur was left, so that the correction for flies maimed by other agency than mine is so small as to be negligible.

It is evident that the finding of flies at any spot need not signify that their breeding-places are near: they might well be some hundred yards away.

With the approval of the Medical Officer-in-Charge I propose to repeat these experiments on a larger scale on the Semeliki River.

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Abore the Mpanga Falls I found no fly, so that it may be argued that the 15 retaken flies had merely returned to their breeding places.

It is noteworthy that of the 192 flies marked on the 9th and 10th 53, or 27'6 per

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cent., were retaken, and of the 101 flies marked on the 12th 28, or 26.9 per cent., were retaken.

DISCOVERY OF PUPE OF GLOSSINA PALPALIS IN NATURAL BREEDING-GROUNDS.

(Abstracts.)

No. II. The accompanying box contains pupæ, 51 in number, found on August 29th and 30th at the camp half-way between Harubale and Bukarungu.

They were lying in loose, dry, friable humus (specimen sent) round and beyond the roots of cultivated bananas on a bank sloping to the lake at distance from the water varying from 4 to 20 yards.

They were not numerous in any one spot, but required prolonged and careful. search. The 51 represent the labour of 15 men for 3-4 hours on the 30th (one only was found on the 29th).

One porter found 14 pupæ.

Empty pupal cases were found in the proportion of 4-1 of occupied ones, and were nearer to, in some cases perhaps on, the surface.

One pupa "hatched out" in a porter's hand as he carried it to my camp, These bananas constitute a belt varying in width from 6-18 yards and about 100 in length. They are backed by dense, woody undergrowth, which extends 100- 200 yards back from the lake. I have searched for pupe in this undergrowth, but up to the present without success.

I am engaged in further investigations.

Amongst the bananas all that is necessary is to gently turn over or rake the humus with the fingers.

No. III. I have since found pupa at Harubale amongst bananas close to the river 250 yards above the ford, and again at Bukarungu in bananas from 5-40 yards from the Nyamakoijo, which here runs at the edge of swampy forest.

No. 1. Under a shrub (Allophyllus) were found 39 occupied and 106 empty pupa cases, and there were probably many more as the search was not exhaustive. A dry bush shaded by the Allophyllus and creepers which had spread over it, covered with vegetable débris and permeated near the surface by a network of root- lets, formed the nursery for these pupa. The majority of the living ones were found at a deeper level than that at which I had sought them before.

cases.

If one found empty cases near the surface and prised up pieces of earth with

a finger one came sometimes on a nest of three or four living ones close together.

On the 10th, after a search in many parts of the woody undergrowth at the river bank, I found pupæ on a steepish slope above a hippo-path, and seven empty

One may for the present say that the larvae are dropped in shade, it may be of shrubs, it may be of bananas, within 45 yards of water, on banks with a decided slope where the surface-soil is loose and friable and partly composed of vegetable débris. The slope seems essential.

The natives who helped me in the search always looked for a bank.

A. G. BAGSHAWE,

Medical Officer,

Sleeping Sickness Extended Investigations.

NOTES ON APPENDIX B.

(1) Breeding Grounds and Pupa of Glossina Palpalis.

The discovery of the breeding grounds by Dr. Bagshawe is most interesting, and may prove to be very important indeed in dealing with the fly and its haunts. If, for instance, the breeding grounds should prove to be confined to definitely circum- scribed areas in which the pupe can be discovered without very great difficulty, or if these localities can be fairly readily recognised by their characteristic physical features or by any other means, this fact would be likely to limit to a considerable extent the areas necessary to be dealt with by clearing and planting, and would thus reduce the expense of dealing with such areas. If, in short, we could attack

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