266 MANUAL OF ZOOLOGY. 



three pairs of legs proper to adult Insects. In these cases the 

 number of legs proper to the adult is not obtained until after 

 several moults, the entire process being stated to occupy in 

 some species as much as two years, before maturity is reached. 



The Myriapoda are divided into three orders viz., the Chi- 

 lopoda, the Chilognatha, and the Pauropoda, 



ORDER I. CHILOPODA. This order comprises the well- 

 known carnivorous Centipedes and their allies, and is charac- 

 terised by the number of legs being rarely indefinitely great 

 (usually from 15 to 20 pairs), by the composition of the an- 

 tennae out of not less than 14 joints (14 to 40 or more), and 

 by the structure of the masticating organs. These consist of 

 a pair of mandibles with small palpi, a labium, and two pairs 

 of " maxillipedes," or foot-jaws, of which the second is hooked, 

 and is perforated for the discharge of a poisonous fluid. There 

 is not more than one pair of legs to each somite, and the last 

 two limbs are often directed backwards in the axis of the body, 

 so as to form a kind of tail. The body in all the Chilopoda is 

 flattened, and the generative organs open at the posterior end 

 of the body. 



Scolopendra (fig. 102), Lithobius, and Geophilus are common 

 European genera of this order. The ordinary Centipedes of 

 this country are perfectly harmless, but those of tropical regions 

 sometimes attain a length of a foot, or more, and these are cap- 

 able of inflicting very severe, and even dangerous, bites. 



ORDER II. CHILOGNATHA. This order comprises the vege- 

 table-eating Millipedes (lulidcR) and the Gallyworms (Polydes- 

 mus). The order is characterised by the great number of legs, 

 each segment, except the six or seven anterior ones, bearing 



Fig. 103. Millipede (lulus). 



two pairs ; by the composition of the antennae out of six or 

 seven joints ; and by the structure of the masticating organs, 

 which consist of a pair of mandibles without palps, covered by 

 a lower lip, composed of the confluent maxillae. The genera- 

 tive apertures are placed in the anterior portion of the body 



In the common Millipede (lulus) the body is composed of 

 from forty to fifty segments, each of which bears two pairs of 

 minute, thread-like legs. The lull of this country are of small 

 size, but an American species attains a length of more than 

 half a foot. 



