580 PHILOSOPHY OF ZOOLOGY. 



that of Rhipiptera, the latter, with more classical propriety, 

 Rhipidoptera (from %mi), in reference to the fanshaped 

 wings. 



II. INSECTA HAUSTELLATA. 



This class includes three Orders. 



Order I. HEMIPTERA. 



The insects of this order exhibit considerable differences 

 with regard to their wings. In some, the upper wings are 

 true elytra, crustaceous or coriaceous, with membranaceous 

 extremities overlapping each other ; while, in others, the 

 upper wings are wholly membranaceous. In some of the 

 genera the males only are winged, or they are all apterous. 

 They agree, however, in the characters exhibited by the 

 parts of the mouth. These are formed for sucking. The 

 labium is produced, with a canal on its upper surface, and 

 consists of several joints. The mandibulae and maxillae ap- 

 pear like four hairs, which, by their union, form the haus- 

 tellum. The labrum is more or less produced as a covering 

 to the base of these organs. The palpi are nearly obliter- 

 ated. The metamorphosis is here semicomplete. This 

 class is divided into two orders, which, in the opinion 

 of some naturalists, ought to be elevated to the rank of 

 classes. 



I. HEMIPTEHA HETEROPTERA. These have the elytra 

 crustaceous at the base, and the extremities folding over 

 each other, and membranaceous. The rostrum is attach- 

 ed to the front of the head. The first segment of the tho- 

 rax larger than the second ; ocelli, two. The Heteroptera 

 admit of subdivision into the terrestrial and aquatic. 



The terrestrial heteroptera have two ocelli, the anten- 

 nae exposed, longer than the head, and inserted between 

 the eyes near the inner margin. Some of these have the 



