CHAP. IX DESCRIPTION OF THE ORDER OF INSECTS. a< 



furnished with jaws. Some of the insects which belong to 

 this sub-order are terrestrial, others are aquatic (as the Large 

 Belostoma, Fig. 162). A very few species are predaceous, 

 others are parasitic, while still others feed upon the juices of 

 various plants (such as the Squash-bug, Fig. 163). 



\DIPTERA (Two-winged Flies). -These insects are providad 

 with only two wings, the posterior pair being represented by a 

 pair of thread-like organs, knobbed at the outer end (such as 

 seen in the Wheat-midge, Fig. 164, and the Onion-fly, Fig- 

 165). These are called balancers or halteres, and are never 

 Wanting, even in those species which are wingless. The mouth- 

 parts are fitted for piercing or lapping. Transformations com- 

 plete. The larvae are destitute of legs (such as the Apple- 

 maggot, Fig. 166, and the larvaa of the Helophilus-fly, Fig. 



Fig. 166. 



Fig. 168. 



167), and are commonly called " maggots;" some are fur- 

 nished with a distinct head (as the larva of the Crane-fly, Fig. 

 168, i) while in others this part is soft, and of no definite 

 shape. The legs, etc., of the pupa (Fig. 168, 2 ) are confined 

 in separate sheaths, but the entire pupa is sometimes enclosed 

 in the hardened skin of the larva (as the pupa of the Apple- 

 maggot, Fig. 76). 



2 

 i 



