520 



FLY MAGGOTS AND MYIASIS 



(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 

 four 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 Castellan! and Chalmers, 

 larva after Blanchard.) 



