496 



ABTHROPODA. 



larvae usually spiny ; pupae hung by a thread, never a cocoon. Species 

 numerous. Vanessa antiopa * lives over winter ; the species of Pieris * 

 attack cabbages, etc.; Papilio,* swallow tails. 



Class V. Diplopoda (Chilognatha). 



The Diplopoda are usually united with the Chilopoda in a 

 group of Myriapoda; but while they agree in having a head fol- 

 lowed by numerous foot-bearing segments, they differ so greatly 

 that no union is possible. The body is nearly cylindrical, although 

 in the Polydesmids by lateral growth it may be flattened above; 

 the legs are close together on the ventral surface, with the tracheal 

 openings near them, while on the sides of the body are other 

 openings of defensive glands, the foramina repugnatoria. 



FIG. 537. 



FIG. 538. 



FIG. 537. Schematic section of Diplopod (compare with fig. 481;. d, digestive tract ; 



y, gonad ; /i, heart ; r, repugnatorial gland ; s, spiracle and tracheae. 

 FIG. 538. Mouth parts of lulus. (After Latzel.) 2, mandibles of 1. molybdinus ; 3, 



gnathochilarium (fused maxillae) of I. luridus. 



A more marked feature is that each segment of the body except 

 the first four or five bears two pairs of appendages, which, with a 

 similar duplicity in chambers of the heart, tracheae, ganglia, etc., 

 shows that a fusion has occurred. The anterior somites bear at 

 most but a single pair of legs; both legs and antennae are short. 

 The head bears, besides the antennae, but two pairs of appendages, 

 a pair of several- jointed mandibles (fig. 538), and a pair of rudi- 

 mentary maxillae fused to a single plate, the gnathochilarium. 



The gonads lie ventral to the intestine far back in the body, those of 

 the right and left sides enclosed in a single sac ; the ducts open separately 

 on the second somite of the trunk. The spermatozoa are not motile. The 

 legs of the seventh segment of the male are used in copulation. The 



