524 



FLY MAGGOTS AND MYIASIS 



and mostly without any serious consequences," Banks gives the 

 following quotation from Walsh, — " Taking everything into con- 

 sideration, we doubt whether, out of 10,000 cases where the larvse 

 of two-winged flies have existed in considerable numbers in the 

 human intestines, more than one single case has been recorded 

 in print by competent entomological authority for the edification 

 of the world." 



Botflies. — There are some flies of the botfly family, (Estridce, 

 which as larvae habitually parasitize the digestive tracts of horses 

 and other domesticated animals, and are especially adapted in 

 habits and structure for such a larval life. 

 They occasionally, though rarely, occur in 

 man. The horse botfly, Gastrophilus equi, 

 for instance, lays its eggs (Fig. 252) on the 

 hairs of horses in spots where they are likely 

 to be licked. The moisture and rubbing 

 of the horse's tongue cause the eggs to 

 hatch at once, and the new larvae, adhering 

 to the tongue, make their way to the 

 stomach and intestine where they attach 

 themselves and develop to full-grown spiny 

 larvae, three-quarters of an inch in length. 

 In the following spring the larvae let go their 

 hold, pass out with the faeces of their host 

 and pupate in the ground. Obviously it 

 could be only by a series of unusual cir- 

 cumstances that these larvae could gain access 

 to the human stomach, yet a number of cases 

 have been recorded. 



— A much more common occurrence in man 

 is infection of the intestine with larvae of various species of house- 

 frequenting flies, especially the lesser housefly, Fannia canicu- 

 laris, and the latrine fly, F. scalaris. The former species is very 

 common in houses both in Europe and America. It closely 

 resembles the housefly but is smaller, and appears earlier in the 

 spring. The peculiar manner of flight, a sudden dart followed by 

 a hovering, is very characteristic and a good means of identifica- 

 tion. This fly is frequently observed hovering about chandeliers 

 hanging near the center of rooms. The eggs are oval, white 

 objects and are laid in decaying vegetable and animal matter 



Fig. 252. Egg of 

 horse botfly, Gastro- 

 philus equi, attached 

 to hair ; gr. , groove for 

 cementing to hair ; op., 

 operculum . (After 

 CoUinge.) 



Fannia Larvae. 



