ARTHROPODS AND MOLLUSCS 



iSS 



Millipeds and centipeds (class Myriapoda). — The Myria- 

 poda are land-animals breathing by means of tracheae 

 like the insects. In them the body-segments are nearly 

 uniform in character with the exception of the head, which, 

 as in the insects, bears the mouth-parts and antenna. There 

 is no grouping of the body-segments into regions except as 



the head is distinct 



from the rest of the 



body. (In a few 



myriapods there 



are indications of a 



division of the hind 



body into thorax 



and abdomen.) 



The presence of 



true legs on all the 



segments of the 



hinder region of 



the body and the 



lack of the three- 

 region division of 



the body are the 



principal external 



structural charac- 

 teristics which dis- 

 tinguish myriapods from insects. 

 The internal anatomy corresponds 

 in general character with that of 

 insects. 



The most familiar myriapods 

 are the millipeds, and the litho- 

 bians and centipeds. The mil- fig. 6S. The skein centiped, 

 lipeds are cylindrical in shape, Scutigera forceps, common 



1 J • r I i r in houses and conservato- 



have two pairs of legs on most of ^^^ (Natural size; after 



the body-segments and are vege- Marlatt.) 



Fig. 64. A galley- 

 worm(milliped) 

 Julus sp. 



