NO. 6 



INSECT ABDOMEN — SNODGRASS 



67 



In the Diplopoda the free basal segment of the leg, judging from 

 its structure and the nature of its articulation with the next segment, 

 would appear to be the coxa, and since the sternal plates of the Diplop- 

 oda surround the bases of the legs, we may conclude with Borner 

 (1921) that the definitive sterna include the subcoxae. Silvestri 

 (1903), however, regards the free basal segment of the diplopod leg 

 as the subcoxa, and the next segment as the coxa, though the latter 



Fig. 27. — Appendages and terminal body structures of Chilopoda. 



A, posterior part of body of Scolopocryptops scxspinosa, telopodites removed 

 except from last segment, showing union of subcoxal sclerites with coxa in large 

 pleural plate {LB) on last pregenital segment. B, ventral view of genital and 

 pregenital segments of Lithobius. C, lateral view of same. D, base of pregenital 

 appendage of Lithobius. E, telopodite of right gonopod of Lithobius, mesal 

 surface. 



An, anus ; Cx, coxa ; C.vpd, coxopodite ; GO, gonopore ; Gp, gonopod ; gS, 

 sternum of genital segment ; GScg, genital segment ; 1st, intersternal sclerite ; 

 LB, limb basis ; IStn, sternum of pregenital segment ; IT, tergimi of pregenital 

 segment; O, levator of telopodite; Prpt. periproct; Q. depressor of telopodite; 

 Sex, subcoxa; Stti, segmental sternal plate; Tlpd, telopodite; iTr, first trochan- 

 ter; 2Tr, second trochanter (praefcmur). 



segment has all the structural features and usual relations of a 

 first trochanter. 



Following the last leg-bearing segment in the Chilopoda comes 

 the definitive genital segment (fig. 27 A, GSeg), beyond which is the 

 periproct {Prpt), or anal segment. According to Heymons (1901) the 

 genital region of the body contains two small somites in the embryo, 

 parts of both of which are sometimes retained in the adult stage. The 

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