NO. 



INSECT ABDOMEN — SNODGRASS 



93 



median caudal filament (cf), a narrow ventral region (D, XlStn) 

 bearing a pair of broad posterior flaps {Papt), and two prominent 

 lateral lobes supporting the cerci {Cer). There can be little doubt, 

 therefore, that the caudal filament and the cerci here belong to the 

 eleventh abdominal segment. The lobes of the eleventh sternum arc 

 evidently the paraprocts (D, Papt). Projecting from beneath the base 

 of the caudal filament (D, cf) is a small median lobe {sa), possibly 

 a remnant of the true telson, represented by the lamina supra-analis of 

 the twelfth segment, better developed in odonate larvae (fig. 12 A, sa). 

 The terminal parts of the abdomen are less simple in some other 

 thysanurans than they are in Nesomachilis. In Thermohia (fig. 7 E, 

 F), for example, the eleventh segment is largely obliterated except 

 for a distinct tergal plate, or epiproct (E, Eppt), which is connected 



Fig. 40. — The cerci and associated parts. 



A, posterior segments of Periplaneta oricntalis, dorsal view, showing union of 

 tenth and eleventh abdominal terga. B, ventral view of terminal segment of 

 same. C, cerci of Hcterojapyx gallardi, and muscles of tenth segment that move 

 them. 



laterally by a pair of small sclerites with the bases of the cerci {Cer). 

 The paraprocts of Theniwbia are large sclerotic plates (F, Papt) 

 supporting the cerci. They would thus appear to correspond with 

 the lateral lobes of the eleventh segment and the median paraproct 

 plates of Nesomachilis (D). A sternal region of the eleventh segment 

 distinct from the paraprocts is not evident in Thermohia. 



In the Dicellura (Campodeidae and Japygidae) the abdominal 

 segments beyond the tenth are obliterated, and the cerci are sup- 

 ported directly by the end of the tenth segment (fig. 40 C, Cer). 



The cerci of the Pterygota most commonly appear to belong to the 

 tenth abdominal segment, since they arise at the posterior edge of 

 the latter, usually from membranous areas inclosed by the adjacent 

 angles of the tenth tergum, the epiproct, and the paraprocts (fig. 12 A, 

 B, Cer). In Periplaneta the cerci of the adult insect arise from be- 



