174 | RHYNCHOPHORA. 
prothorax when viewed from above varies, and is scarcely available by itself as a 
diagnostic. character; in one or two species, e. g. Hewacolus glaber, the head is as 
much covered as in the majority of Tomicides. A reliance upon this, the character 
usually employed to differentiate between the Hylesinid and Tomicid groups, has led 
to the few described genera of Hexacolides being referred by their authors to very 
diverse positions. While Pycnarthrum and Heaacolus have been described by Eichhoff 
as Tomicides, the former was placed by Chapuis in the Hylesinides under the name 
Nemobdius. On the other hand, Ferrari described a species of Pycnarthrum doubtfully 
as a Hypoborus (H.? hispidus), but he rightly regarded his own genus, Scolytodes, which 
is scarcely distinct from Hewxacolus, as intermediate between the Tomicides and the 
groups with an exserted head. By Chapuis Scolytodes was made the type of a “sub- 
tribe,” next to the Camptoceri, under the name Ctenophorus. 
The Hexacolides thus form a group not far removed from the Tomicides, and it may 
be argued that they are as appropriately included in that somewhat heterogeneous 
assemblage as are genera like Crypturgus and Aphanarthrum. This must remain a 
matter for individual opinion ; but it cannot be denied that, with the possible exception 
of Microborus, a small and peculiar form of Crypturgus-like appearance, the genera 
here associated are of close relationship. The species are confined to and apparently 
common in the Neotropical region, the few forms described here being no index to the 
number of those existing without names in collections. 
The Central-American species received by us are divisible into five genera, which 
may be distinguished as follows :— 
Eyes approximate on the gular surface; anterior femora very large, much longer 
than the others. 
Eyes approximate on the front; sides of the prothorax sinuate about the middle ; 
body subglabrous . . . - 5 © © © © es ew ew Microborus. 
Eyes not approximate on the front ; sides of the prothorax not sinuate ; * body 
pilose or squamose. . . . . Soe eee ee ew ee ee) Pycnarthrum. 
Eyes remote below, not extending on to the gular surface; anterior femora not 
very large, about equal in length to the others. 
Tibie broadly dilated towards the apex, strongly serrate above; prosternal 
process transverse . . . . woe ee we ew we ww ee ) 6Prionosceles. 
Tibie not broadly dilated towards the apex, finely serrate above; prosternal 
process not transverse. 
Side-margin of the prothorax well defined; tarsislender . . . . . Hexacolus. 
Side-margin of the prothorax nearly obsolete behind, replaced towards the 
apex by a large pubescent impression ; first three tarsal joints vertically 
compressed 2. 1 ee we ee ee eee ee ww ee Epomaddius. 
