38 Psyche [April- June 



tenth tergite " ep " in the sawfly shown in Fig. 17. In most sawflies, 

 the ninth tergite "9*" is greatly reduced, and the tenth tergite 

 "ep" (Fig. 17) unites with it. In the siricid shown in Fig. 17, the 

 basal sclerite "p" (interpreted as the tenth sternite by some 

 entomologists) may possibly represent the plate labeled "p"in 

 Fig. 11 of the ephemerid — though it is also possible (but not as 

 probable) that the segment "g" of the genital claspers of the 

 siricid shown in Fig. 17 represent the styligers "p" of the ephem- 

 erid (Fig. 11). In either case, the styliger region "p" of the 

 sawfly (Fig. 17) would be distinct from the ninth sternite "ha" 

 thus approximating the condition exhibited by Gryllohlatta cam- 

 podeiformis, which Walker considers unique in having styligers 

 distinct from the ninth sternite. The two-segmented clasping 

 forceps "s" composed of the segments labeled "g" and "h" in the 

 sawfly shown in Fig. 17, may represent the claspers labeled "s" 

 (and also composed of two segments labeled "g" and "h" — which 

 however may not be the exact homologues of the segments bearing 

 these labels in Fig. 17) in Fig. 11 of the ephemerid.^ The penis 

 valves "pv" composing the penis or phallus in the sawfly shown 

 in Fig. 17, doubtless represent the penis valves "pv" of the 

 ephemerid shown in Fig. 11. The saw^y group, or Prophymenop- 

 tera, is thus seen to have retained the primitive condition of the 

 parts as nearly as any of the higher forms have done, and a study 

 of the parts in the sawflies is therefore of considerable importance. 



In the Mecopteron shown in Fig. 19, the tergite labeled "ep" 

 doubtless represents the tergum of the ninth segment, while the 

 tenth tergite has either united with it, or has become greatly 

 reduced. The ninth sternite "ha" is well developed, and the 

 gonopods are composed of two segments "g" and "h" which are 

 possibly homologous with those bearing the same labels in Fig. 17. 

 The sclerite labeled "p" in Fig. 17 apparently unites with the 

 pleural region of the ninth segment in the Mecoptera (Fig. 19) ; and 

 in the insect shown in Fig. 19, the penis valves, which are usually 

 separate in the lower forms, have probably united to form the 

 single membranous structure "pv." In the Mecopteron shown 

 in Fig. 21, the plate "pp" represents the ventral and lateral 

 portions of the ninth segment, while the ninth tergite becomes 

 prolonged into two lobe-like processes labeled "sg," which are 



' The parameres of Dermaptera and Coleoptera are also homologous with these structures. 



