IV. INSECTA: HEXAPODA 



403 



poison claws. Their terminal joints are sharp and contain the ducts of 

 poison glands. The spiracles (at least a pair to e\'ery other somite 

 except those of the head) are lateral in position in the soft integument 

 between the dorsal and ventral plates (tergum and scutum) (fig. 439). 

 The heart is elongate, with chambers in each somite (fig. 67); there are 

 two large Malpighian tubes, and the nervous system is elongate, with 

 ganglia in each somite. The unpaired gonads are dorsal to the intestine, 

 while the single duct opens ventrally in the preanal somite. 



Fig. 440. Fio. 441. 



Fig. 440. — Mouth parts of Scolopendra morsitans. i, antenna;; 2, mandibles; 3, 

 maxilla; (gnathochilarium) ; 4, second ma.xilla: (labium); 5, poison feet. 

 Fig. 441. — Scolopendra morsitans, centipede (after Schmarda). 



LiTHOBiiD^, 15 leg-bearing somites; certain dorsal plates enlarged and 

 overlapping the succeeding somites; Lithobius,'* etc. Scolopendrid^, centi- 

 pedes; at least 17 legs and s ocelli; Scolopendnr^- (fig. 441). GEOPHiLiDiE, not 

 less than 30 pairs of legs, spiracles 2 less than legs. Gcophilus* Scutigerid^, 

 legs very long, 15 leg-bearing segments, but only 8 dorsal plates. Sculigera* 



Sub Class II. Hexapoda. 



The Hexapoda is by far the largest division of the Arthropods, 

 containing at least ten times as many known species as aU the rest. The 



