3io 



COLLEGE ZOOLOGY 



a pair of maxilla. One pair of antenna (i) and either simple or 

 aggregated eyes (2) are usually present. There are olfactory 

 hairs on the antennae and a pair of scent glands in each segment, 

 opening laterally (4). The breathing tubes (trachea?) are usually 

 unbranched; they arise in tufts from pouches which open just 

 in front of the legs. The heart is a dorsal vessel with lateral ostia ; 

 it gives rise to arteries in the head. The two or four excretory 

 organs are thread-like tubes (malpighian tubules) which pour 

 their excretions into the intestine. 



The millipedes move very slowly in spite of their numerous 

 legs. Some of them are able to roll themselves into a spiral or 



ball. They live in dark, moist places 

 and feed principally on vegetable sub- 

 stances. The sexes are separate, and 

 the eggs are laid in damp earth. The 

 young have few segments and only 

 three pairs of legs when they hatch, 

 and resemble apterous insects (Fig. 

 259). Other segments are added just 

 in front of the anal segment. Ex- 

 amples: Jnlus (Fig. 232), Polydesmus, 

 Spirobolus. 



Order 3. Chilopoda. — The Chilop- 



ODA are called centipedes (Fig. 233). 



The body is flattened dorso-ventrally, 



and consists of from fifteen to over 



one hundred and fifty segments, each 



of which bears one pair of legs except 



the last two and the one just back of 



the head. The latter bears a pair of 



poison claws (Fig. 233, Kf) called maxillipeds, with which 



insects, worms, mollusks, and other small animals are killed for 



food. 



The internal anatomy of a common centiped is shown in Figure 

 234. The alimentary canal (n) is simple; into it opens the ex- 



Frc 233. — A centipede, 

 Lilhobiusjorficatus. Kf, poison 

 claws. (From Sedgwick's 

 Zoology, after Koch.) 



