76 GENERAL ZOOLOGY 



any receptacle where water is left standing long enough for 

 the eggs to develop into mature mosquitoes. 



Crane Flies. The crane flies (Fig. 51) look so much like 

 mosquitoes that many people mistake them for an extremely 

 large race of bloodthirsty mosquitoes. In fact, they are un- 

 able to bite. 



The Hessian Fly. The Hessian fly (Phytoph'aga destruc'tor) 

 is a small gnat-like fly (Fig. 52) which appeared in this 

 country soon after the Revolution. It is thought that it 

 was brought over from Europe in straw transported by the 

 Hessian soldiers. The young (Fig. 52, c) develop in the 

 stems of wheat, rye, and barley. Here they do so much 

 damage that it is estimated that more than 10 per cent of 

 the wheat crop is destroyed by this fly in an ordinary year. 



Definition of Diptera (Gr. dipteros, "two- winged")* The 

 insects collectively called flies agree in the possession of two 

 wings, the place of the posterior pair being taken by the 

 halteres, or balancers, which may therefore be considered 

 reduced wings. Although a few other insects have but a 

 single pair of wings, the flies alone possess halteres. The 

 flies belong to the order Dip'tera. The Diptera have the 

 mouth parts fitted for sucking or piercing. They undergo 

 complete metamorphosis. The larvae are commonly known 

 as maggots. 



