8o 



THE HOUSE FLY 



It must not for a moment be assumed that every Biting 

 Stable Fly introduces the germs of some form of disease 



FIG. 21 



(A) WING OF A HOUSE FLY (Musca domestica}. Note the sharp 

 elbow in the third long wing vein (i) and compare it with the 

 same vein in the Stable Fly. 



(B) WING OF A STABLE FLY (Stomoxys calcitrans). The third long 



wing vein (2) is less bent than that in the wing of the House 

 Fly. It also has a sharp lancet for puncturing the skin of its 

 host. The House Fly, on the contrary, has a soft proboscis 

 or sucker. 



(From a drawing by Mr. Ignaz Matausch in the American Museum of 

 Na turn I History , Wash ing ton . ) 



into its host when it punctures it with its lancet. When 

 the insect sucks the blood of a beast sick with an infectious 



