412 ZOOLOGY. 



in insects, properly so called, and consist only in the forma- 

 tion of new rin^s, and in a corresponding augmentation in the 

 number of the limbs. 



550. Two natural groups, easily distinguished by the 

 form of the antennae, compose this latter class namely, the 

 chilognathus or iulus, and the chilopodes or the scolopendra. 



Fig. 407. lulus. 



The chilognathi have a cylindrical body, and feed on organic 

 matters more or less decomposed ; their pace is slow, and they 

 often roll themselves into a spiral or ball. They are known 

 by the names of iulus (Fig. 407), polydesmus (Fig. 408), and 

 of glomeris 



Fig. 407 (408) . Polydesmus, Lat. lulus complanatus, Fab. 



The chilopoda have the body flattened and more mem- 

 branous than the preceding; they are carnivorous, and run 

 verv fast. Three principal genera compose this group : the 

 scolopendra (Fig. 141), the lithobius, and the scutigera. 



OF THE CLASS ARACHNIDA. 



J551. The class of the arachnida is composed of art it -u- 

 animals, having a strong analogy with insects, and, 

 like them, organized to live in air, but which may be distin- 

 guished at once by the general form of the body, and l>v the 

 number of their limbs; they differ also from those animals in 



