Affinities of Ptfivonsii'cys regalis. 443 



and consequently has described the male Pteronarcys as the female, and the 

 latter as the male. He seems to have been led into this very error, which he 

 points out as having been committed by others *, by confining his attention 

 chiefly to Perla, in which he correctly says that the reproductive organs 

 "in the males open at the extremity of the abdomen, whilst in the females 

 the entrance of the oviduct is under the eighth ring." This description is 

 perfectly true, as a matter of fact, both in Perla and Pteronarcys. Never- 

 theless, M. Pictet has confounded the sexes of the latter, by mistaking the 

 prehensile appendage of the male for a supposed ovipositor of the female, 

 which does not possess such an organ, but in which the outlet of the oviduct 

 is situated in the eighth segment, precisely as in Perla, as I have found on 

 examination of specimens of this sex oi Pteronarcys regalis (fig. 17) now in 

 the cabinets of the British Museum. 



The body of the female P. regalis (fig. 17), and of other species of this 

 genus, is easily distinguished from that of the male. The segments are more 

 depressed, are much broader than long, and altogether are less elegant in 

 form. The terminal tenth segment is considerably wider than in the male, 

 and is only partially divided longitudinally on the under surface into two 

 valves, each of which is marked with an imperforate spiracle, the situation of 

 the caudal branchiae in the larva. The valves are united at their base, and 

 are separated throughout the remainder of their length only by a slight 

 sulcus. The female organs open externally in the eighth segment (fig. 17. 8), 

 which has its ventral surface divided longitudinally into two plates, which 

 cover the entrance to the oviduct. The margin of the segment, in some 

 specimens, is simply notched in the middle, at the point of junction of the 

 plates, as in the one delineated ; but in others there are two minute processes 

 at the angles of the notch, the rudimentary representatives of corresponding, 

 more elongated parts in the male, which, united, form the process of the 

 eighth segment (fig. 16. 8). These parts, which are of their smallest size in 

 the females of this, are much larger in those of other species. In the original 

 specimen of P. hiloba, now in the British Museum, and correctly regarded by 

 Mr. Newman as a female, not only the margin, but a large part of each plate 

 is included in two triangular curved lobes, from which the species is named. 



* Loc. cit. p. 37. 



