DIPTERA. 



I8 9 



house fly, but probably a stable fly, which looks a good 

 deal like a house fly and frequently comes into the house 

 and bites you, possibly because you taste better than its 

 usual food. The stable fly has stylets for piercing epi- 

 dermis, while the house fly can only lap its food. (Fig. 

 78.) The harmfulness of the house fly comes from 

 another habit; it gets its supply of food from exposed 

 decaying substances, and it is not at all particular as to 



FIG. 77. FIG. 78. 



FIG. 77. A stable fly. (Three times natural size. Kellogg.) 

 FIG. 78. Mouth parts of a house fly. (Kellogg ) 



what that substance is, generally the contents of slop 

 pails, spittoons, or filth found elsewhere in places where 

 filth is left exposed. The disease germs found in sputa 

 of tuberculous persons, or the agents of putrefaction 

 found wherever decaying matter is left lying in the air, 

 are taken up on the hairy feet of these flies as they crawl 

 about these places in search of food or to lay their eggs; 

 and if their next visit is to your dining-room table where 

 food is sitting, or to some abrasion in your skin, woe to 

 you as to the possible results. (Fig. 79.) House flies 

 undoubtedly spread infectious diseases by carrying the 

 germs of those diseases in the filth which adheres to 



