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point out that my theory as to the effect of persecuting the game during the latter part of the dry season receives support in this connexion. The general greater scarcity of fly during the present season I am inclined to attribute to the effect of last dry season's operations. It is to be noted that last July "fly" proved to be very scarce indeed in the area, and that although some increase in certain spots has occurred since then, conditions have apparently not been sufficiently favourable for any great increase to take place during what is probably the optimum period for the insect, namely, from August to the advent of soaking rains. The operations have apparently to a large measure kept the game away from the fly haunts, notwith- standing the general increase in numbers of the former.

The portions of the area where there is a noticeable diminution of fly since last year include: (1) The whole area south of the Shangani from Ngondo Salt Pan to the Gwaai-Shangani junction. In the whole of this strip which is about thirty miles in length, I only saw and captured two tsetse flies, one of which was on the Gwaai River close to the Shangani Junction and the other opposite the Mzola- Shangani Junction. The Bushu Salt Pan, where I have always seen fly, if only one. previously, appears both from my own observations and the hunters' reports to be entirely free from fly at present, and the same remark applies to the strip of forest close to the river between this pan and the Sibone-Shangani Junction. Here I took two flies last year. In general fly has been sufficiently prevalent to be met with regularly in this region throughout the operations, but has steadily decreased practically to the vanishing point., Mr. Bishop, who has been hunting this region during the present season has dealt with the game in such a way that increase, assuming the dependence of "fly on game, is unlikely. The single specimen, female taken on the Gwaai River, may have followed us down the Shangani, but Bushu Salt Pan is really only about a mile and a-half from the Gwaai River, and it is not possible to map fly as closely as this in broken country. I have for some time regarded the Gwaai River as practically infested at this part (see my previous reports).

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The south side of the Shangani between the Sibone Junction and the main camp has yielded no fly since 1920, and apparently maintains its freedom. Specimens are sometimes taken on the south bank by parties which have crossed from Lubimbi Salt Vlei and are presumably followers (see report of Officer in command for September, 1922). In the series of vleis near the river above the main camp, I took three flies last year, but this year only one during a careful search. Above this point no fly were seen at all, even at Ngondo Salt Pan where Mr. Henkel and myself were attacked by a numerous swarm in October, 1920. No fly were seen also between Ngondo and Sebasinungu's Kraal, and the natives informed us they had entirely disappeared. A few fly were present at Ngondo last year. Although somewhat beyond the region of effective shooting, this spot was temporarily the site of the main camp early in 1921, and was afterwards much more hunted than in former years. Hunters stationed at F post on the Shangani have paid considerable attention with [?] during the present year. The forest round the salt pan is com- paratively open, and it apparently constitutes one of the fly centres, like that close to Capt. Brereton's main camp in 1919, whence elimination of both game and fly is a comparatively easy matter.

(2) The northern side of the Shangani from the Sibone Junction through Lubimbi Salt Vlei and Bira River to the Main Camp. Between the Sibone Junction and Msolozi along the north bank of the river I took only one fly (a male) this year. Last year several were in general encountered. At Lubimbi Vlei this year I took three males only, although we halted and made tea there. Only one (a male) was taken at the crossing of the Bira River and one (male) close to the old hunters' camp at Bira Shawu. None were seen between this camp and the main camp. On a similar round last year I took 17 fly (14 males and 3 females). You will recall the large numbers of tsetse present in this part in 1920.

(3) Up the Kana River. As stated in my previous reports I cannot regard the Upper Kana Post at the Palm Pan as a very good index on account of the situation of a hunting camp at the pan and the consequent "following in" of the fly from elsewhere. Last veár I took no fly at the pan and only saw one in several hours on the river below the pan. At that time the camp had been unoccupied for several months. This year the post has been occupied. We saw no fly on arrival, although my caravan was immediately attacked by numbers in 1919 and in a lesser degree in 1920. Natives going down to the river for water brought back two female flies,

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however, and next morning I dawdled along the river for half an hour and caught two males and two females. After that we proceeded down the river again, and a further male was taken on the path, probably carried. In the neighbourhood of Bondo Hill on the Kana the fly seems practically to have disappeared. Mr. Smith, the hunter stationed here, reports their absence from the Kana in this part, although they occurred there in some numbers as late as 1920. On the present trip we halted for breakfast on two occasions at the crossing, where I casually caught 23 flies on the upward and downward journeys in 1920, and saw none at all on either occasion. I may mention that in 1920 we made no halt here, and the flies were simply picked up as we passed by. In October last year I caught one female only between the Upper Kana Post and Bondo Hill, and saw none at all at the crossing.

The only part of the area where tsetse appears to be definitely more abundant than last year is on the lower part of the Mzola River at the spot known as Mzola Index No. 1. Here there is a considerable amount of young green grass, which is, of course, very attractive to grazing animals. Mr. Kemp informed me that little game had been shot here, but I personally saw two impala at the index and three kudu very close to it. The soil in these parts is usually too hard to leave a good spoor, but tracks of game were numerous in the vicinity. Two days' work at Mzola Index No. 1 gave a male density of 3.25 as against .75 last year, and a female percentage of 23.5 per cent, as against 77.5 per cent. last year. In reality with two nets working two hours in all 13 males and 4 females were caught as against 3 males and 10 females last year, so that the actual catch of flies was only four in excess of last year, but the higher proportion of males gives a considerably higher figure.

With regard to Mzola Index No. 2, which is on the south side of the river opposite Index No. 1, I visited this spot twice at an interval of three days. On the first occasion we did not cover a large area but caught 7 males and 4 females. Three days later Mr. Kemp and myself collected assiduously working gradually down to the Mzola-Shangani Junction and caught only 8 flies in all (6 males and 2 females). On this occasion we covered much more ground and occupied much more time than on any previous visit. These figures can be compared more or less with 16 flies (10 males and 6 females) caught in October last year, and 74 flies (38 males and 36 females) caught in 1920, although the figures are, of course, not strictly comparable. The clear point is that this spot has shared in the general reduction of fly in the area and that reduction has been at least maintained during the present year.

It may be mentioned that I found fly along one short strip of the Shangani River where I have not seen it previously. This is in the north bank between the Main Camp crossing and the Mzola Junction, a distance of some 2 miles. The bush here is somewhat thick and haunted by bushbuck and baboons, the latter very numerous. A new path was opened up this year leading obliquely eastward across the river from the camp. On reaching the further side where a tributary stream enters, I caught 2 males and 2 females on the first occasion, but saw none on the return journey. Two days later I caught one female at the same spot, and returning the same day along the north side from the Mzola Junction I caught 4 males and 2 females, of which 2 males and 1 female were taken in the tracks of a troop of baboons which had just crossed our front, and one male was taken at the spot diagonally opposite the main camp which has already been mentioned. It is nossible that this strip may have become infested with flies following parties to the main camp from the Mzola, but in any case this strip of forest is almost con- nected with the infested portion of the Mzola River, and the fly may have spread along naturally.

In order to make the position clear at a glance the following tables indicate the number of fly collected at different points or along definite lines in October of different vears during or preceding the operations:

(1) Bushu Salt Pan and Country South of Shangani from Gwaai: Shangani

Junction to Sibone Confluence.

1919 1921. Fly alwavs met with in small numbers here and there in traversing this tract and at least a single fly met with at the Salt Pan. Noticeable decrease in 1921,

1922. No flv seen at Salt Pan or elsewhere in vicinity, but a single female teken in Gwaai River about a mile above the Junction.

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