312 Annals Entomological Society of America [Vol. XII, 



imperfectly chitinized and not coherent, though an ineffective 

 engagement between the ventral and inner valves may occur ; 

 basivalvulse very widely separated and rotated outwards, con- 

 nected in front by a chitinous arch or bar ; dorsal valvules cover- 

 ing inner pair, their bases greatly expanded, and medially united; 

 superior intervalvula connected with dorsal valvulae and with 

 lamella formed by united bases of inner valvulee, which are free 

 from ventral valvules and lack an intervalvular membrane ; infer- 

 ior apophyses represented by slender bars connected with a 

 vestigial inferior intervalvula ; cerci of moderate length, flattened, 

 segmented; supra-anal plate absent in adult, being substituted 

 by tenth tergite ; paraprocts flattened, generally well chitinized 

 in part. 



Nymph with valvulae terminal, dorsal pair broad and flat, 

 retaining styli until last stage; a vestigial supra-anal plate 

 present. 



Isoptera — Abdominal segments somewhat flattened; seventh 

 sternum forming a large subgenital plate, covering the remaining 

 sterna; eighth sternum ill-defined and greatly reduced; ninth, 

 oblique or almost horizontal; valvifers, when present, widely 

 separated from tergites, the intervening space not crossed by an 

 apodeme; ovipositor absent or represented by a very reduced 

 pair of ventral valvulae and traces of the bases of the dorsal 

 valvulas; tergites eight, nine and ten laterally narrowed, the 

 tenth replacing the supra-anal plate, which is absent in 

 the adult; paraprocts broad, somewhat chitinized; cerci short, 

 slender, with 2-5 segments. 



Dermaptera — Tergites of segments eight and nine greatly 

 abbreviated and concealed by the seventh, tenth very large; 

 seventh sternum forming a subgenital plate and concealing 

 eighth and ninth sterna, which are medially divided; ovipositor 

 usually absent, when present, reduced and lacking inner 

 valvulae; ventral valvulae long and slender, dorsal valvulas 

 shorter and broader; tenth sternum sometimes represented by 

 a pair of small sclerites; cerci very large and strong, forcipate, 

 unsegmented (except in larvae of some genera) ; supra- anal 

 plate terminal, exposed, heavily chitinized, divided into 

 pygidium and telson, sometimes with an intervening meta- 

 pygidium; paraprocts ventral, consisting of flat, well-chitinized 

 plates. 



