CLASS INSECTS. 



381 



suction is composed of the same elements, but a little dif- 

 ferently arranged. The mouth is armed with a tubular and 

 cylindrical bill or beak, directed 

 downwards and backwards (Fig. 

 360), and composed of a sheath 

 enclosing four stylets ; the sheath 

 (a, Fig. 361) is in its turn formed 

 of four joints, placed end to end, 

 and represents the lower lip; 

 finally, the stylets (b c), which 

 have the form of slender filaments, 

 stiff and serrated at their sum- 

 mit, to enable them to pierce the 

 skin of animals or the tissues of 

 plants, are the representatives of 

 the mandibles and jaws, ex- 

 tremely elongated. In the hemip- 

 tera which live at the expense 

 of animals, the bill is in general ^g. 359. 



very strong, and folded into a 



semicircle under the head. In those which are nourished on the 

 juices of vegetables, it is, on the contrary, almost always 



J 



1 



Fig. 360.-The Wood-Bug. 



x b c 



Fig. 361. Buccal Apparatus of a 

 Hemipterous Insect. 



slender, and applied in repose against the inferior surface 

 of the thorax between the limbs. Its length is sometimes 



