Affinities of Pteronarcys 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 bis attention 
ants 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 of 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 brancbiz 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 
speciinens, 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 pean 
at the angles of the notch, the rudimentary representatives of corresponding, 
more elongated parts in the male, which, united, form the pue P " 
eighth segment (füg.16.8). These parts, which are of e smallest nse in 
the females of this, are much larger in those of other species. In the original 
Specimen of P. biloba, 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 tr iangular curved lobes, from which the species is named. 
* Loc. cit. p. 37. 
