Observations relating to the transmission of sleeping sickness in Uganda, the distribution and bionomics of Glossina palpalis, and to clearing measures / by Aubrey D.P. Hodges.

  • Hodges, Aubrey Dallas Percival, 1861-1946.
Date:
1909
Catalogue details

Licence: In copyright

Credit: Observations relating to the transmission of sleeping sickness in Uganda, the distribution and bionomics of Glossina palpalis, and to clearing measures / by Aubrey D.P. Hodges. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    tlie number ami percentages of those re-taken elsewhere. The small niimhei ol 1) ami h flies re-taken may he attributed to the shortness of the ])eriod in which they could bo caught. The table shows that male and female flies travel ecpially. Table II shows what number of flies marked at each place were retaken at other places and where. It will be noticed that while 10 WA Hies were recaught at A, only 3 LA flies were recaiight there. A proportion of 5 to 3.° The nu’mbem are small but tend to show the great part taken by boats in carrying Gl.palpalis. There was much traffic of small dug-out canoes between ’WA and A. The same thing is brought out by the C figures. Not only were flies caught here identified as having come from 5 out of 6 possible places but the propoi'tion of marked flies caught was much higher than anywhere else. C was not in a fly area but boats came to this, the camp landing place from all parts. At D and F flies were caught on one occasion only. The table shows that two flies travelled two and a quarter miles, one one and three quai'ters, two one and a half, one one and a quarter and eight one mile (the distances are not overestimated). Of these long-distance flies nine were male and five female. It will be noticed that while thirteen travelled down stream only one travelled up stream. This fact loses its significance when it is observed that on the five occasions on which upstream flies could be caught 552 were examined whereas on the three occasions on which down-stream flies could be caught only 145 were examined and also that 635 flies were marked above (at A and B) and only 258 below (D and F). None the less one would expect a greater number of flies to be conveyed down stream than up for boats make quicker passages with the current and therefore carry flies twice the distance in the same or less time, and such flies as alight on floating islands are invariably taken down stream. I have underlined the bank to bank flights to distinguish them at a glance from the along-bank flights. Leaving out of account WA to A where a homing instinct might play a part it is noticeable that the majority of flies which crossed did not do so between the nearest points on opposite banks; thus there were no fliglits between WA and B, none between D and C, nor between D and E. This is additional evidence that flies ar’e conveyed across for the most part by boats, for if they got across by their unaided efforts one would expect them to choose the shortest passages.* Conditions Influencing Flight of Flies. Boats.—In my opinion by far the most important. I have watched a fr/.settled on a small dug-out canoe remaining * It also goes far sliow that O. polpa/i-i docs not make such long (lighls as would be necessarj to cross this river, and then-fore that such a river is an efficient barrier in the absence of boats. An observation vvliicli 1 made on the Semliki at the edge of the great forest is of interest in this connection. On one side of tlie river were three native huts close to the bank. Fl,v was scarce, 18 wore caught in three hours ; on the otlier bank, uninhabited, 48 were caught in two hours, weather conditions being the same. The stream was 70-80 yards wide. If O. could cover this distance in a single (light the (lies should have been at least as numerous on the inhabited side, where bleed was always to be had during the hours of activity of the fly.
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