. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. posited, sometimes deep in the decajdng material selected, in small batches of from two to half a dozen, until from 25 to 50 or more are laid; there are a number of such depositions made by a single fly during her life. The eggs hatch in from two to five days, usually three, into whitish, almost transparent footless mag- gots (Fig. 242A) very similar to those of the housefly, but easily distinguishable by the position of the posterior stigmal plates (see Fig. 243). The larvae mature in a minimmn of from
. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. posited, sometimes deep in the decajdng material selected, in small batches of from two to half a dozen, until from 25 to 50 or more are laid; there are a number of such depositions made by a single fly during her life. The eggs hatch in from two to five days, usually three, into whitish, almost transparent footless mag- gots (Fig. 242A) very similar to those of the housefly, but easily distinguishable by the position of the posterior stigmal plates (see Fig. 243). The larvae mature in a minimmn of from 12 days to over two months, usually in about 15 to 20 days, and crawl into drier por- tions of the breeding material to pupate. The pupse (Fig. 242B) are olive-shaped, chestnut-colored ob- jects, one-fourth of an inch in length. With favorable temperatures the adult fly emerges in from six to ten days, but this period may be much prolonged by cold weather. The shortest time in which a stable-fly may develop from the time of egg-laying is about three weeks, and this is extended under conditions which are not ideal. According to Herms' experiments, the average length of life of stable-flies is about 20 days. They sometimes live several months, however. There are several other genera and species of the famfly Muscidae which sometimes bite man, but none of them are habitual feeders on human blood, and they are hardly Fig. 241. Eggs of stable-fly, Stomoxys calcitrans. X 20. Note eggs natural size in upper corner. (After Newstead.). worthy of special consideration. Fig. 242. Larva U) They all and pupa (B) of stable- resemble Stomoxys in general appearance, ^^' ^'""^"^y^ caidtrans. ° 1^X4- (AfterNewstead.) though some, notably the common hornfly, Hoematobia serrata (or Lyperosia irritans), are much smaDer. Their Ufe histories are in general like that of Stomoxys, though there is some variation as regards choice of breeding places. Manure of various kinds is selected b
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