40 



MISC. PUB. 601, U. S. DEPT. OF AGRICULTUPvE 



Figure 37. — Lepidoptera. The Indian-meal moth (Plodia interpunctella (Hbn.)), 

 a common pest of stored grain. Actual length about 11 mm. 



DIPTERA 



Diptera (flies, mosquitoes, gnats, and their allies) are usually 

 winged, but have only one pair of wings with not many veins; the 

 hind wings are represented by a pair of slender, knobbed structures 

 called halteres. The mouth parts are formed for sucking or piercing 

 and sucking. (See figs. 3S and 39.) The immature stages are worm- 

 like and are usually known as maggots ; they are entirely unlike the 

 adults. The order includes forms that are parasitic, others that are 

 predaceous, and others that live on either living or dead plant material. 

 Because many of the species carry diseases, this is one of the most 

 important orders from the standpoint of human welfare. Other mem- 

 bers of the order cause a great amount of damage to crops. 



Figure 38. — Diptera. 



Sarcophaga hacmorroidalis (Fall.), 

 length about 15 mm. 



a flesh fly. Actual 



