Further reports (no. 5) on flies as carriers of infection.

Date:
1912
Catalogue details

Licence: In copyright

Credit: Further reports (no. 5) on flies as carriers of infection. Source: Wellcome Collection.

    22/30 (page 18)
    The Latrine Fly, F. scalaris Fah. Tliis species which, on account of its most usual breeding habits, may be called the Latrine Fly, is very common both in European countries and in North America. Owing to its general similarity it is often confused with the Lesser House-fly F. canicularis, but the chief differences have already been indi- cated. In the adult male of F. scalaris black is the prevailing colour; but the humeri are light-coloured. The legs are black and the middle femur is swollen ventrally, bearing on its broader side a group of brush-like bristles as will be seen from Fig. 1, a. The middle tibia is provided, as shown, with a dis- tinct tubercle near the distal end. The colouring of the female is more distinctly grey with a faint longitudinal striping on the thorax. F. scalaris is slightly larger than F. canicularis, measuring up to 6 mm. in length. Tlie habits of this species are somewhat similar to those of F. canicularis, but it prefers excrementitous matter as a nidus for the eggs and is very commonly found breeding in human excrement. It has been recorded breeding in human excrement by Schiner, Taschenberg, Howard and Newstead, and I have also bred it from this material in England and Canada, both in privies where the excrement was found in a semi-liquid con- dition and on rubbish tips or dumps where it was mixed with ashes or clinker. Taschenberg also refers to its breeding in mushrooms. In 1908, Dr. David Sharp submitted the larva of this species to me for examination. He had found it in rotting fungus in the New Forest in September, 1905, and noticed its similarity to Swammerdam’s “ Latrine Larva.” The larvae emerge as early as eighteen hours after the deposition of the eggs and the larva becomes full-grown in six to twelve days. The shortest time which I have recorded for the pupal stage was nine days, which was in the month of August, but I believe that under very favourable conditions the pupal stage would be passed in a shorter time. The larva of F. scalaris. The larva of this species (Fig. 3) has a general resemblance to that of F. canicularis, but a closer examination will reveal the very marked differences and a number of distinguishing charac- ters. In shape it is similar to the larva of F. canicularis, being compressed dorso-ventrally.- The appendages, or processes, how- ever, are very different. The pair of antenna-like processes at the anterior and upper edge of the second segment are much shorter than those of F. canicularis, as will be seen from the figure where they are shown dorsal to the oral lobes. On the dorsal side of the larvse, from segment III. to segment XI., is a series of nine pairs of short and somewhat thick processes of a very spiny character; the first two pairs being little more tban spinous tubercles. Viewed from above the larva is seen to be surrounded by a fringe of feather-like processes,