AMERICAN COLEOPTERA. 227 



or exposed face of the front and middle tibiae, and the manner of 

 punctuation of the metasternum have proved of the highest service 

 in breaking up what would otherwise have still remained an un- 

 wieldy complex. In the large majority of species the front tibiae 

 are bistriate externally, the grooves being usually marginal, but 

 occasionally more approximate. In a i'ew species one or the other 

 of these grooves may become greatly reduced or entirely lost. In 

 about half of our species the middle tibiae are striate or sulcate ex- 

 ternally along their posterior margin. The punctuation of the 

 metasternum is, like that of the upper surface, more or less 

 obviously dual in nature, consisting of smaller and larger punctures 

 intermixed. In the disposition of the larger punctures, and these 

 may be the only ones visible without a strong glass, we have a very 

 useful character; these being sometimes confined to the middle of 

 the metasternum, sometimes denser at middle, but extending sparsely 

 to the side margin, or again they may lie nearly uniformly scattered 

 over the whole surface. These characters are probably subject to 

 some individual variation, but I have thus far found them remarka- 

 bly constant, Additional characters useful in specific separation are 

 not very numerous and consist chiefly in the bodily form which 

 varies from rather strongly elongate (carinatum, longulum) to 

 broadly oval (palliatum, latum ) ; the outline in profile, which mav 

 be perfectly symmetrical (validum, indistinctum) or distinctly gib- 

 bous or more strongly arched anteriorly (abbreviatum, gibbufum) ; 

 the vestiture so dense as to completely conceal the surface (pallia- 

 turn), or so sparse as to be scarcely detectable (castaneum, politum \ 

 with every intermediate degree. The eighth antenna] joint exhibits 

 a moderate amount of variation, from the elongate triangular form 

 in uniform' and luteotectum to distinctly transverse in graeile and 

 castaneum. The relative size and abundance of the intermixed 

 coarser punctures of the upper surface is of considerable specific 

 importance, but is subject to individual variation. External sexual 

 marks are virtually lacking. In a few species there is an evident 

 difference in the size of the eyes, and in one (castaneum) the eighth 

 joint of the antennae is of different form in the two sexes. In a 

 small number of species (metasternale, carinatum and punctatum), 

 all of elongate form, the metasternum is acutely longitudinally cari- 

 nate at middle In punctulatum the terminal joints of both labial 

 and maxillary palpi are deeply emarginate at apex, after the man 



TRANS. AM. ENT. SOC. XXXI. Jl/LY, 1905. 



