Further reports (no. 6) on flies as carriers of infection.

Date:
1913
Catalogue details

Licence: In copyright

Credit: Further reports (no. 6) on flies as carriers of infection. Source: Wellcome Collection.

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    Experiment 4.—26tli-29th July, 1912. 1,500 red-coloured Hies were liberated from tlie roof of the Medical Schools at 9.30 a.m. on July 26tli. The weather was warm and fine, and a moderate breeze was blowing'. The lly which travelled the longest distance (400 yards) would appear, from the chart, to have travelled with the wind, and so consti- tute an exception to our rule, but as the fly was caught early on the morning of the 27tli it had, therefore, mainly been sub- jected to the wdnd of the previous day. In this case it travelled in a N. by W. direction, whilst the wind of the previous day was W.S.W. We would also call attention to the fact that this entailed passing through the most thickly-housed part of Cam- bridge. One of our most striking instances of flies travelling deliberately against the wind is that afforded by an individual which wras found in a trap 325 yards distant in a W. by 8. direction, only 1J hours after the time of liberation, although the wind w-as blowing steadily the whole time five miles an hour in a W.S.W. direction. \_See Chart 4.] Experiment 5.—29th July-lst August, 1912. 1,500 orange-coloured flies were liberated at 11.15 a.m. on July 29th. In all our previous experiments the flies were liberated at an altitude of 45 feet, but in this case they were set free on the ground. The temperature was somewhat lower than on the previous occasions, and it was raining slightly at the time of liberation, so that it is not surprising that only six flies were recovered. In spite of the very strong wind (12 miles per hour) that was blowing throughout the w^hole period of the experiment, the two dies that travelled the longest distance were both recovered at a point S.W. by W., whilst the wind was from S.S.W. to W. [See Chart 5.] Experiment 6.—6th-12th August, 1912. 2,400 red-coloured dies were liberated from the ground at 11.30 a.m. on August 6th. A strong wind (11 miles per hour) was blowing at the time of liberation, and several showers fell during the day, but nevertheless, no less than 34 dies were re- covered at distances ranging up to 325 yards from the point of liberation. It will be noticed that most of the 15 dies wrhich travelled a distance of more than 150 yards, had down either across, or in the teeth of, the wind prevailing on the day pre- vious to their recovery. In this case, a number of dies were recovered from rooms at an altitude of 30 feet, and in many cases the insects must have down over buildings at least 50 feet high.
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