1922] Walker: Structure of Orthopteroid Insects 11 



SPECIAL MORPHOLOGY. 



In describing the male genitalia and associated parts in the 

 various orders it will be convenient to take them in a different 

 sequence from that followed in the discussion of the female 

 organs. 



Ephemerida. 



This group is remarkable for several reasons. The pro- 

 longation of the supra-anal plate into a jointed caudal filament 

 or cerciform appendage ("telofilum, " Crampton), similar 

 to that of certain Thysanura has been already referred to in 

 Part I. The cerci are longer than in the females, but are 

 otherwise similar. The paraprocts are unchitinized and are 

 covered by the 10th tergum, there being no distinct 10th 

 sternum. 



The 9th sternum is very large and is usually divided trans- 

 versely into two separate plates, of which the distal one is 

 prolonged into a pair of processes, divided into several segments 

 and serving as claspers. These processes are generally con- 

 sidered to be jointed styli, but it is possible that the terminal 

 segments alone represent the styli, the remaining segments 

 belonging to the coxites, which are also represented by the 

 distal of the two sternal plates (the coxale), the proximal one 

 being the sternite. The fact that these structures serve as 

 claspers in copulation and that in Grylloblatta the coxites are 

 apparently claspers lends some support to this view. Moreover 

 they contain muscles, which in the Thysanura and Orthopteroid 

 insects only reach the bases of the styli. In some cases the 

 coxites are completely separate, as in Blasturus nebulosus Walk. 

 (PI. I, Fig. 2) or Callihaetis ferrugineus Walsh. (PI. I, Fig. 4), 

 i. e., the distal plate is divided by a median suture. In others 

 {Heptagenia spp.) a tripartite division is slightly indicated, the 

 two stylus-bearing parts being indistinctly separated by a 

 median area. 



There are two penes, whose walls may be wholly mem- 

 branous or accompanied by parameres. In Callihaetis ferru- 

 gineus, e. g., (PI. I, Fig. 4) these take the form of slender 

 chitinous bands, extending from the lateral margin of the 10th 

 tergum obliquely mesad and cephalad to the bases of the 

 penes, thence curving along the lateral margins of the penes 



