CHAPTER VII 



THE FLIES: DIPTERA 



. . . like small gnats and flies as thick as mist 

 On evening marshes. SIIKLLEY. 



House-Flies and Flesh-Flies. The common house-fly (Mus'ca 

 domes' tica, Fig. 37) is a cosmopolitan insect. The eyes are 

 very large, occupying the whole side of the head; the an- 

 tennae are short and composed of only three joints, the third 



bearing a bristle. 

 The mouth-parts 

 are formed for 

 sucking and lap- 

 ping. They consist 

 of a short tongue- 

 like proboscis, with 

 large oval flaps, or 

 lobes, on each side. 

 These flaps are 

 extensile, and are 

 roughened like a 

 file on the inner 

 surface, thus per- 

 mitting of their 

 use as a scraper, 

 by means of which the insect can lap up sweets or other food. 

 The proboscis is made up of the united maxillae. The thorax 

 is globular and bears but one pair of wings, though the rudi- 

 ments of others, called " balancers," can be seen in the form 

 of two little round objects, borne on slender stalks. These 



58 



FIG. 37. Metamorphosis of House-Fly. Enlarged 



