300 Annals Entomological Society of America [Vol. XII, 



This is a secondary deposit of chitin and does not represent a 

 definite sclerite. It is not present in all Blattidag. 



A narrow chitinized strip possibly represents the tenth 

 sternum in Parcoblatta. The supra-anal plate is wholly absent 

 in the adult though its vestige is present in the young nymph. 

 The paraprocts, on the other hand, are large, broad and rather 

 flattened and the dorsal surfaces strongly chitinized. The cerci 

 are of the usual Blattid type, the basipodite developed on the 

 inner instead of the outer side. 



The immature Blattid (e. g., Parcoblatta, Figs. 55-57) is 

 remarkable for the very primitive condition of the ovipositor, 

 which is indicated, (1) by the fact that the valvulae all develop 

 from the hind margins of their corresponding segments; (2) in 

 the manner in which the dorsal valvulce develop (vide infra) ; 

 (3) in the broad flat form of their valves, as distinct from the 

 slender inner and ventral valvulce (cf. the Thysanura, Fig. 72), 

 and (4) in the persistence of styli on the dorsal valvulae until 

 the last moult. 



Development of the ovipositor {Parcoblatta). The stages here 

 outlined were first described by Denny ('94)-" in the case of 

 Blatta orie?italis L. and are well known, but their significance 

 has not been sufficiently emphasized. Figs 55, 56, 57 and 58 

 represent ventral views of segments eight and nine, a portion 

 of seven (the seventh sternum being nearly all removed), of 

 three immature stages and the adult Parcoblatta pensylvanica. 

 The youngest nymph (Fig. 55) differs little from the male of 

 the same stage except in the presence of a pair of small pro- 

 cesses, on the hind margin of the eighth sternum and a small 

 apical median fissure of the ninth sternum. Both sterna are 

 well developed. In the next stage (Fig. 56) the eighth sternum 

 is much narrower; the two little processes are greatly elongated 

 and are marked off from the sternum by a slight constriction. 

 They are now distinguishable as the ventral valvulee, and the 

 basivalvulse are also indicated in the median sternal region. 

 The two stylus-bearing lobes into which the sternum is divided 

 have become relatively narrower, and the fissure between them 

 has greatly deepened and widened at base, from which the 

 rudiment of the inner valvulae have arisen. 



20 Denny, A., Rept. 63, Meeting Brit. Assoc. Adv. Science, p. 818 (1894). 



