1922] Walker: Structure of Orthopteroid Insects 43 



The opposite extreme is seen in Blatta or Periplaneta, in 

 which there are two lobes, separated by an obhque fissure, 

 each bearing several chitinous plates, prolonged into a variety 

 of peculiarly shaped processes, none of which are capable of 

 being invaginated. In such cases it is exceedingly difficult 

 to determine which of these processes are homologous with 

 those of BlatteUa, or even the homologies of the right and left 

 lobes of the same species; but the complex folding of the lobes 

 suggests that the various plates and processes have arisen 

 secondarily as chitinizations of the folds surrounding the sheath 

 of the primary process. As these two processes arise primitively 

 dorso-lateral to the aedeagus, as can be seen in the nymph, it 

 seems reasonable to consider them tentatively as the parameres 

 of which some representative would be expected to occur in so 

 generalized a group as the Blattoidea. 



The following species were studied in detail: BlatteUa 

 germanica L, Parcoblatta pensylvanica DeGeer, Blaberus afropos 

 Serv., Periplaneta bninnea Burm., P. Juliginosa Brunn. and 

 P. americana (L.)- 



BlatteUa. germanica L. (PI. IX, Figs. 80-83). In this species 

 the tenth tergum is produced into a large flexible flap, the ninth 

 sternum is very asymmetrical and the styli are unequal in size, 

 close together and both to the left of the mnddle line. The 

 paraprocts are asymmetrical and divided into two parts, a 

 small membranous, pubescent lobe, next to the anus, and below 

 this a transverse chitinous strip, which meets the edge of the 

 tenth tergite and bears a prominent hook. The dextral hook 

 curves upward and is simple, the sinistral hook curves down- 

 ward and is bifid. The penis is large and somewhat conical 

 and the ejaculatory duct opens upon a long, straight, retractile 

 spine or virga. 



The dextral paramere consists of the following structures: 

 An irregular pocket with folded walls, which is produced 

 internally into a long slender apophysis, whose outer extremity 

 is bifurcated. Articulating with its outer branch and forming 

 a prolongation of the ectodorsal edge of the pocket is a pro- 

 jecting blade or shaft, and connected with the inner branch 

 is a chitinous strip, forming the ventro-mesial edge of the 

 pocket. A rounded lobe with a chitinous margin is folded into 

 the pocket on its inner side and serves for the origin of pro- 

 tractor muscles, which are inserted into the inner side of the 



