COLEOPTERA. 151 



great majority of the species, the table can only be relied on as an 

 approximate guide to the descriptions. 



On comparing our species of this genus with those of Europe, we 

 find a remarkable difference in regard to the proportional numbers of 

 those with margined and unmargined abdomens. Of the former the 

 European fauna contains more than four times as many as it does of 

 the latter, while in the North American representatives, the ratio of 

 those with margined abdomen to those in which the border is absent 

 or very rudimentary, is about one to nine. Several species in our 

 fauna have the margin entirely obsolete on all the segments except 

 the first, where it is distinctly visible ; these are all included in the 

 division with abdomen unmargined. It is, to be remarked that our 

 fauna does not contain any forms with spotted elytra. 



The species occurring north of the Mexican boundary in North 

 America may be provisionally classified as follows : — 



* Abdomen margined. 



Legs black ; tarsi sometimes paler. 



Tarsi pale testaceous 1. retl'USllS. 



Tarsi scarcely paler than the tibiae ; pubescence longer, more dense, and 

 much more conspicuous. 

 Prothorax widest behind the middle ; elytra strongly undulated. 



2. fraternus. 



Prothorax widest slightly before the middle : sides less angulate ; elytra 



scarcely undulated 3. umbratilis. 



Legs pale brownish-testaceous, clouded with dark castaneous at the junction 

 of the femora and tibiae; size much smaller 4. ci'oceatlis. 



** Abdomen not margined, <>r extremely narrotoly and imperfectly so. 



Fourth abdominal segment wider than the first 5. ildveiia. 



Abdominal segments decreasing in width posteriorly, sometimes having the 

 first three or four sub-equal in width. 

 Head broad, much wider than the elytra ; elytral suture shorter than the 

 pronotum. 



Prothorax widest before the middle. Virginia 6. eill'Ops. 



Prothorax widest at the middle. Florida 7. Iliegalops. 



Prothorax widest far behind the middle ; much smaller species. Massa- 

 chusetts 8. lugens. 



Head moderate or small in size ; elytral suture longer than the pronotum. 

 Large species, not less thai! 3.6 mm. in length. 

 Legs black throughout. 



Prothorax widest behind the middle ; sides thence very feebly con- 

 vergent and nearly straight anteriorly. Vancouver Island. 



9. plicipemiis. 



Prothorax widest in advance of the middle. 



