Further preliminary reports on flies as carriers of infection.

Date:
1909
Catalogue details

Licence: In copyright

Credit: Further preliminary reports on flies as carriers of infection. Source: Wellcome Collection.

    7/46 (page 5)
    o that one often sees the flies present in mills quite white in colour. This, however, met with failure, as the flies soon shook themselves free of the flour. Next was tried rice starch powder, as it was thought that being a finer powder, it might adhere better than the flour. Equally futile results attended experiments with this method. Subsequently, ordinary coloured black-board chalks were finely ground up with a pestle and mortar, and dusted on to the flies. The dusting was accomplished by placing the balloon containing the flies in a paper bag, pouring in the ground-up chalk, and gently shaking it about. By this means the flies became completely covered with chalk, and immediately proceeded to clean themselves, commencing with the eyes. They never succeeded however in removing the chalk from the upper portion of the thorax, nor from the base of the wings. A series of balloons were treated in the above fashion, with different coloured chalks, and the flies were then liberated, either in net cages, or about the laboratory. Some of the flies liberated in the laboratory were, in one instance, still to be seen six days later, but for the most part they escaped through open windows and doors, and not being liberated in sufficient numbers, the results were not definite. Those confined in large netting cages gave more satisfactory results. In these cages, the flies were practically under natural conditions, having a large open space, and plenty of light. The flies were fed with sugar and water. For convenience the results are given in tabulated form, so that they may be seen at a glance. Experiments with coloured Chalks and Dyes* Colour July 23 July 24. July 25. July 26. July 27. July 28. Dark Blue ... 50 flies dusted Few Few None Red 50 flies dusted Few None Light Blue ... 50 flies dusted Few Few Few None White 50 flies dusted Many Many None Yellow 50 flies dusted Many Many Many Few Few Yiolet 50 flies dusted Many Many Few None Rosin, Alcohol and Rice Starch. 50 flies dusted Very few None Orange G. Al- cohol and Rice Starch. 50 flies dusted Very few None * These flies were liberated about the laboratory, but unfortunately not in sufficient numbers for the results to be at all definite.