CHAPTER VIII 



THE FLIES: DIPTERA 



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

 On evening marshes. 



Shelley 



House Flies. The common house fly (Mus'ca domes'tica, 

 Fig. 47) is a cosmopolitan insect. The eyes are very large, 

 occupying the whole side of the head; the antennae 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 ex- 

 tensile and are roughened like a file on the inner surface, 

 thus permitting 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 bears but one 

 pair of wings, though the rudiments of others, called bal- 

 ancers or halteres, can be seen in the form of two little 

 round objects, borne on slender stalks. These balancers 

 also act as organs of hearing. Two broad scales are found 

 on the sides of the thorax, just behind the wings. The 

 legs are fitted for running. The pulvilli are large and bear 

 tubular hairs, which secrete a sticky fluid, by means of 

 which the fly can walk on smooth surfaces, even when up- 

 side down. 



The eggs, over one hundred in number, are laid usually 



in horse manure or garbage. They hatch within a day into 



smooth, white, almost transparent, conical, footless larvae, 



called maggots. The rudimentary mouth parts consist only of 



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