INSECTS AND DISEASE 



383 



for rasping and reducing to a liquid or semiliquid condition 

 the material upon which it feeds. The mouth parts of the 

 stable-fly, on the contrary, form a strong piercing beak which 

 can cut through even the toughest skin in order that the fly 

 may suck the blood of its victim. Persons are often bitten by 

 flies that they believe to be house-flies. But house-flies cannot 

 bite, and it will usually be found that the culprits are stable- 



FIG. 170. Stable-fly, Stomoxys calcitrans. Resembles house-fly in 

 general appearance, but has pointed, piercing and sucking beak, and the 

 vein which terminates near the tip of the wing is not so sharply angulated 

 as in the house-fly. (See Fig. 166.) (Five times natural size.) 



flies. If the wings of a house-fly and a stable-fly be carefully 

 compared it will be seen that the fifth vein (counting from the 

 front margin) of the house-fly's wing is bent forward at a con- 

 siderable angle while the corresponding vein in the wing of 

 the stable-fly is only slightly curved. The fourth and fifth 

 veins are the two veins that end near the tip of the wing. In 

 the house-fly the tips of these veins are very close together; in 

 the stable-fly they are rather widely separated. 



