1922] Walker: Structure of Orthopteroid Insects 41 



a process, which lies in a fold of the right lobe. This process is 

 slightly grooved mesially, the groove being continued along the 

 interlobar fissure. Possibly this is a seminal groove, the process 

 bearing it being a sort of rudimentary ^deagus, similar to many 

 blattids, such as Periplaneta. In this genus, and in other Blat- 

 tids, Mantids and Phasmids, the ejaculatory duct is more 

 closely associated with the left lobe than the right. 



Nymph. In the immature male of Grylloblatta the coxites 

 are more nearly alike in size and form, although the asymmetry 

 is evident in the specimens studied. These evidently belong to 

 two successive instars, the later of which appears to belong to 

 about the penultimate stage. 



In the younger nymph (Fig. 66) the tenth segment is rel- 

 atively large, its sternal surface being nearly in the same plane 

 with that of the ninth. The supra-anal plate and paraprocts are 

 much larger and more prominent than in the adult. The left 

 coxite is distinctly larger than the right and the latter show^s 

 no trace of the spur present in the adult. The tenth tergum is 

 symmetrical and without free prolongations of the ventrolateral 

 margins. Between these margins is a distinct, though small and 

 membranous, tenth sternal area. In the intersternal mem- 

 brane are two oval, slightly elevated areas, which are the 

 rudiments of the two genital lobes. 



In the older nymph (Figs. 67, 68) the tenth segment is 

 relatively somewhat smaller and the tenth sternal area almost 

 obliterated by the closer approximation of the ventro-lateral 

 margins of the tergum. The supra-anal plate and paraprocts 

 have decreased in size. The genital area is no longer horizontal 

 but sub vertical in position, and the genital lobes are much 

 larger and separated by an oblique fissure, as in the adult, but 

 there are as yet no chitinous processes nor eversible sac. The 

 ninth sternum, coxites and styli have not changed appreciably, 

 though there is a slight increase in their asymmetry. 



Blattoidea. 



In the male cockroach the abdominal terga, cerci and cereal 

 basipodites are essentially like those of the female. The eighth 

 and ninth terga are abbreviated, while the tenth replaces the 

 aborted supra-anal plate and is often considerably prolonged 

 caudad. It is however, narrowed on the sides, terminating 

 beneath the bases of the cerci. The ninth sternum forms a large 



