The house-fly : Musca domestica Linn. its structure, habits, development, relation to disease and control / by C. Gordon Hewitt.

  • Hewitt, C. Gordon (Charles Gordon), 1885-1920.
Date:
1914
Catalogue details

Licence: In copyright

Credit: The house-fly : Musca domestica Linn. its structure, habits, development, relation to disease and control / by C. Gordon Hewitt. Source: Wellcome Collection.

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    down to form small deeply-staining spherical bodies. This histo- logical degeneration begins at the distal ends of the tubules, which in the mature larva usually have the appearance shown in fig. 55 (m.t.); all the stages of degeneration can be truco-d out. This process may be a means of getting rid of the remaining larval excretory products. The Respiratory System. The tracheal system (fig. 59) of the adult larva consists of two longitudinal tracheal trunks united by anterior and posterior com- missures, and communicating with the exterior by anterior and posterior spiracles; the latter are situated in the middle of the oblique caudal end, and the anterior spiracles, which are not present in the first larval instar, are situated laterally at the posterior border of the third body-segment. I believe that the anterior spiracles (a.sp.) are true functional spiracles, though for some time I was inclined to share Lowne’s opinion that they were not functional. This latter view was due to the fact that it was difficult to understand how these spiracles could obtain air when they are immersed, as they usually are, in the moist fermenting materials on which the animal feeds. A care- ful microscopic examination of their structure, however, strengthens my belief that they are able, if necessary, to take in air; the occasions when this is possible are probably not infrequent. Each of the anterior spiracular processes consists of a fan-shaped body (fig. 44, a.sp.) bearing six to eight small papiliform processes. The papillae (fig. 47) open to the exterior by a small pore which leads into a cavity having a clear lumen surrounded by branched cuti- cular processes, whose function is probably to prevent solid particles from penetrating the spiracular channel. The body of the fan- shaped spiracular process is filled with a fine reticulum of the chitinous intima, which Meijere (1902) calls the “felted-chamber (Filzkammer); through this mesh work the air can pass to the longitudinal tracheal trunk. The posterior spiracles (fig. 61, p.sp. and fig. 62) are D-shaped with the corners rounded off and their Hat faces are opposed. Each consists of a chitinous ring having, internal to the Hat side, a small