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.

    8/46 (page 6)
    Experiments icith coloured Chalks. Flies confined, in large Net Cages. Colour. 30 July. .SlJuly. 1 Aug. 2 Aug. 3 Aug. 4 Aug. 5 Aug. 0 Aug. 7 Aug. Net. 1. Violet. 40 flies dusted. Fed on sugar and water. 9 dead (22'5 per cent.). 3 badly battered. Colour good. 6 dead (15 per cent.). Colour good. 2 dead (5 per cent.). Colour fading. 2 dead (5 per cent.). Colour very faded. 1 dead (2'5 per cent.). Colour gone. Net •->. Light Blue. iO flies dusted and fed as in Net 1. 5 dead (125 per cent.). Colour good. 6 dead (15 per cent.). Colour good. None dead. Colour fading. 1 dead (2‘5 per cent.). Colour very faded. 5 dead (12'5 per cent.). Colour gone. Net 3. Yellow. 40 flies dusted and fed as in Net 1. 5 dead (22‘5 per cent.). Colour good. 2 dead (5 per cent.). Colour good. 2 dead (5 per cent.). Colour good. 4 dead (10 per cent.). Colour fading. None dead. Colour very faded. 1 dead (2'5 per cent.). Colour very slight. 11 dead (2‘75 per cent.). Colour very slight at base of wings only. Rest dead (27’5 per cent.). Colour gone. The coloured flies, confined in nets, giving good results, the following isolated net experiment was also started:— Date. Mortality. Per cent. Remarks. 31st July 25 flies dusted with “ hrick-red ” chalk. 1st August 5 2‘) Colour very good. 2nd „ 3 12 3rd „ 4 16 4th „ None — V 11 5th „ 1 4 11 11 6th ,, None — Colour growing fainter. 7th „ — Colour still distinct. 8th „ — 11 9th „ 2 8 n 11 10th 2 8 11th „ None — ri »> 12th „ — fi 11 13th „ — 11 11 14th ,. 4 16 15th „ 3 12 11 11 16th „ None — 11 11 17th „ n — M >> 18th „ — 11 )1 19th „ 1 4 11 11 It will be seen from the above table that the colour remained distinct for twenty days. This result is highly satisfactory, as it shows that the colour can remain upon the fly during the greater part of its normal adult existence. Why this ‘■^brick-red chalk gave better results than the other chalks, it is difficult to say. Possibly some injurious property present in the other chalks was absent in this one.