Casey — A Revision of the American Paederini. 43 



Hesperobium Csy. 



The dentition of the mandibles will at once distinguish this 

 genus from Gastrolobium, there being but two large elongate 

 sharply pointed and much less unequal teeth, instead of the 

 three teeth of the latter genus. The two teeth of the right 

 mandible are clearly and evenly outlined throughout, but the 

 lower tooth of the left mandible has a small shallow notch 

 and vestigial tooth-like inequality of the edge far down on its 

 lower side. The species, which are less numerous than those 

 of Gastrolobium, differ considerably from the latter in facies, 

 and, except in a few aberrant forms, in their sombre black or 

 piceous coloration, longer basal joint of the antennae and 

 type of male sexual modification, no trace of the folds, foveae 

 or lobe of the second and third ventrals ever being observable. 

 They appear also to be exclusively confined to temperate and 

 boreal North America, not extending below the Mexican 

 boundary and inhabit the entire country from the Atlantic to 

 the Pacific, being the only genus of Cryptobia, except 

 ^6a5ac^i(s, forming part of the true Pacific coast fauna. It is 

 therefore the ancestral stem-forms of this genus, in all prob- 

 ability, rather than the preceding that, migrating in remote 

 times to Asia by way of Alaska, have gradually become the 

 present Monocrypta, 8pirosoma, Ilomoeotarsus and Cryj^to- 

 bium of Asia and Europe. The species are tolerably homo- 

 geneous but sell at um, perfectly normal otherwise, differs 

 greatly in its pale elytra, maculate with black, and cribratum 

 and rubripenne in some features of form and coloration, as 

 well as the pale, very coarsely and sparsely sculptured elytra, 

 call to mind the remarkable type of Lissobiopsio be described 

 below. The various species may be distinguished by the char- 

 acters given in the following table : — 



Basal angles of the head more or less evident, the head more oblong; elytral 

 punctures never very coarse, alsvays close -set and never with more than 

 a trace of serial arrangement at any part 2 



Basal angles of the head obsolete, the sides converging from the eyes to the 

 neclc and almost evenly arcuate; neck not more than three -fifths as wide 

 as the head; elytral punctures extremely coarse, sparse and more or less 

 distinctly serial in arrangement ; surface polished throughout 13 



