. Animal parasites and human disease. Parasites; Medical parasitology; Insects as carriers of disease. (Fig. 250B) are white, footless creatures, provided with a pair of stout hooks near the mouth, and with bands of minute spines which give them a screwlike appearance, whence they derive their name. Eating away at flesh and even bone, they develop rapidly to a length of about half an inch, and maturity may be reached in three days, though four or five days is usually required. When fully developed the larva leaves its feeding grounds and buries itself in loose earth nearby, where it pupates in
. Animal parasites and human disease. Parasites; Medical parasitology; Insects as carriers of disease. (Fig. 250B) are white, footless creatures, provided with a pair of stout hooks near the mouth, and with bands of minute spines which give them a screwlike appearance, whence they derive their name. Eating away at flesh and even bone, they develop rapidly to a length of about half an inch, and maturity may be reached in three days, though four or five days is usually required. When fully developed the larva leaves its feeding grounds and buries itself in loose earth nearby, where it pupates in two or three days. The pupae are brown in color, and shaped somewhat like olives. After f<5ur days or more in the pupal case the adult insect emerges, climbs up on nearby herbage and rests in a characteristic position with the head down. The whole life cycle occupies from nine days to two weeks or more. As remarked before, the female screw-worm fly, about to re- produce, is attracted to any animal smell and frequently finds a suitable place for egg-laying in exposed wounds, or in the nose or ears of people sleeping out doors, especially in case of foul-smell- ing catarrh. Sometimes the flies select recently vacated Der- matobia nests, boils, sores, etc., for the young to develop in. As soon as hatched the maggots begin eating their way into the tissues with which they are in contact, using their strong man- dibles as nippers for cutting flesh and even bone. From the ear they may make their way into the inner ear, completely de- stroying the auditory apparatus. From the nose they penetrate to the pharynx, frontal sinus, the eye-ball, and even the brain, occasionally doing such extensive damage as to cause death. Usually an abundant discharge of pus and scraps of tissue, in- tense pain, and delirium accompany the infestation. A severe. Fig. 250. Screw-worm fly, Cochliomyia (or Chrysomyia) macellaria, adult and maggot. X 3. (Adult after Castellani and Chalmers, larva after Bla
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Keywords: ., bookcentury1900, bookdecade1920, bookpublishernewyo, bookyear1922
