78 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 95 



extension of the paraprocts between the lower edges of the tenth 

 tergum (B, Papt) suggests that the sternum of the tenth segment has 

 been correspondingly displaced forward. The penes have the same 

 position in larval mayflies (M, Pen) as in the adult, but the accessory 

 structures are only weakly developed in the larva. Concerning the 

 development of the penes in Ephemeroptera, Palmen (1884) says 

 the larval vasa deferentia become attached to the body wall at the 

 posterior border of the ninth segment, and at the points of attachment 

 the penis rudiments grow out carrying with them the ends of the ducts. 

 The writer is indebted to Dr. Jay R. Traver, of Cornell University, 

 for named specimens amply representing the principal variations in 

 the male organs of Ephemeroptera, on which the preceding descrip- 

 tions are based. 



DERMAPTERA 



Among the Dermaptera there appear to be retained the same two 

 primitive features of the reproductive system found in the Ephemer- 

 optera, namely, the location of the female genital opening immediately 

 behind the seventh abdominal sternum, and the independence of the 

 male exit ducts, which may open separately on a pair of penes. The 

 lateral oviducts of female Dermaptera, however, come together in a 

 short median oviductus communis, while in the male the independence 

 of the gonoducts is never as complete as in the Ephemeroptera. and 

 the paired penes are united upon a common basal plate that forms a 

 large flat apodeme for muscle attachments. In many forms, more- 

 over, the intromittent organ is a single penis with either a pair of 

 outlet ducts, or a single complete duct. The external genitalia of 

 Dermaptera have been described by Meinert (1868), Jordan (1909), 

 Heymons (1912), Zacher (1911), Burr (1915', 1916). Crampton 

 (1918), Walker (1922), Snodgrass (1935). 



A dermapteran intromittent organ of the double type occurs only 

 in the Labiduroidea. The two penes here present are concealed in a 

 deep genital chamber above the long ninth abdominal sternum. Their 

 bases arise close together (fig. 27 A) from the anterior wall of the 

 genital chamber {-v-x) where they are united upon a common apode- 

 mal plate {Ap) extending forward. Each penis {Pen) consists of a 

 basal stalk bearing two distal lobes, and is traversed by a ductus 

 ejaculatorius (Dej). The median lobe (a) is the true terminus of the 

 penis and contains an eversible end-sac (preputial sac, c), into which 

 the ejaculatory duct discharges; the lateral lobe (b) is an accessory 

 process, or paramere, of the penis. A long slender rod, or virga, 

 usually accompanies each ejaculatory duct, its apical part being pro- 



