Further reports (no. 4) on flies as carriers of infection.

Date:
1911
Catalogue details

Licence: In copyright

Credit: Further reports (no. 4) on flies as carriers of infection. Source: Wellcome Collection.

    8/52 (page 6)
    this must be due rather to the habits of this fly than to the failure of other species to breed on the tip, since the collection of 200 larvae and pupae from fresh tip refuse gave the following results •— Musca domestica ... ... ... ... 143 Muscina stabulaus ... ... ... ... 34 Calliphore erythrocephala ... ... 18 Pollenia rudis ... ... ... ... 3 Homcilomyia, canicularis ... ... ... 2 A considerable number of undetermined Phoridce were also bred out from samples of the refuse which were kept as likely to be good for some of these larvae. We see, therefore, that there was a considerable variety among the flies breeding in the refuse ; just as on the sewage farm Sepsis and Scatophaga were the dominant species, so Musca domestica preponderated on the refuse heap; but in most cases other species were also present. The comparatively small number of flies usually observable on the actual refuse might possibly be taken as strengthening the case against their being attracted from the surrounding district by the smell of the refuse, since in that event we might not unreasonably expect that the refuse would be chosen as a resting-place as often as the hut. except perhaps on cold days. Although a few of the marked flies mentioned below remained in and about the hut for as long as a week in some instances, there was no evidence to show that they ever returned after having once left the refuse-heap. The bearing of these minor observations on the question whether the tip was to be regarded primarily as an attracting or as a dis- tributing centre may be summarised. Flies were extremely abundant in the village from the third week of June, 1910, some two months earlier than the usual time of their appearance in this country. No unusual conditions were found in the village itself, but a refuse-tip half-a-mile away had been started in the previous January. The suggestion that flies were attracted to the tip, and tarried in the village on their way thither, was rendered improbable by the facts that— (1.) The number of flies actually to be seen at any one time on the refuse was not noticeably great. Marked flies which had once left the heap did not apparently return to it. (2.) In spite of the great number of larvae and pupae in the refuse, it was very difficult to discover any eggs el- even newly-hatched larvae. (The period between the collection and the dumping of the refuse varied from 12 to 48 hours. In one case a considerable number of flies were seen to escape when the hatches of a barge were removed after being closed down for two days.) (3.) The flies caught at the tip showed no preponderance of females such as might, a priori, be expected from the analogy of some other Muscid flies. In the case of Homalomyia, all of the first lot were males, which