268 RHYNCHOPHORA. 
PTEROCYCLON. 
Corthylus, Erichson, Wiegm. Arch. ii. 1, p. 64 (pars)*; Ferrari, Borkenk. 1867, p. 49 (pars) *. 
Monarthrum, Kirsch, Berl. ent. Zeitschr. 1866, p. 213 *, 1868, p. 214*; Leconte and Horn, Rhynch. 
N. Am. p. 347°. 
Corthylomimus, Ferrari, Borkenk. 1867, p. 48°. 
Cosmocorynus, Ferrari, ibid. p. 62”. 
Pterocyclon, Eichhoff, Berl. ent. Zeitschr. 1868, p. 277°, 1869, p. 299°; Rat. Tom. p. 487”. 
? Trypocranus, Kichhoff, Rat. Tom. p. 435™. 
The species of Pterocycion are cylindrical insects, of moderate or considerable length 
in proportion to their width. The antenne possess a two-jointed funiculus and a 
rather small club, which is normally oval or obovate, with straight or curved sutures ; 
its apex is not acuminate, as in Brachyspartus. 
Exceptionally the club is reniform (P. scrobiceps), subtriangular, or broadly triangular 
(P. fimbriaticorne) ; these characters, when they occur, are probably distinctive of the 
female. 
The prothorax is obliquely declivous in front and rather finely asperate; its hind 
angles are margined by a lateral line which extends forward almost to the apical border. 
The prosternum is short. The elytra are separately rounded at the apex, and divaricate 
or emarginate at the tip of the suture, exposing the pygidium; the emargination is 
usually shallow and the sutural margins, though separated, are not excised ; there is 
a rounded angle where they meet the apical border. The declivity is either convex 
and impressed along the suture or more or less excavate, as in Tomicus, with very 
variable armature ; but the apices are furnished at most with a narrow reflexed margin, 
and are never explanate or produced. The anterior tibiew are curved, slightly widened 
apically; their superior margin is serrate, and their outer face is granulate or 
porcate. 
The sexual characters are important. In few species have both sexes been observed, 
and in those the chief secondary character is the presence in the female of a fringe 
of hairs on the antennal club. That this is a female character has been shown for 
P. fasciatum and P. mali by Hopkins (Canad. Ent. 1894, p. 275). It is here assumed 
to hold good wherever found, but its constancy has not been proved by dissection. The 
elytra may be similar in both sexes, but in the female the declivity is usually less impressed 
or excavate, with weaker armature. Out of fifteen forms in our collection which are 
without any fringe on the antennal club, eleven have the elytral declivity excavate ; 
whereas out of ten forms with an antennal fringe, presumably females, but one has a 
decided apical excavation (P. lobatum). ‘The head is usually simple in both sexes, but 
is excavate, fringed with long curled hairs, or otherwise variously constructed in the 
females of a few species (P. lobatum, P. ferrari, P. Jimbriaticorne). The second of 
