THE MONoTOMM) P.KKTLES. 667 



The principal paper treating of (lie family is by 



Horn." Synopsis of the Monotomidas of the United States," in 



Trans. Amer. Ent. Soc., VII, 1879, 257-267. 

 In Henshaw's list the genera are (by mistake?) combined with 

 those of Trogositidce. Eighteen species, distributed among five 

 genera, represent the family, as far as known, in the United States. 



KEY TO INDIANA GENERA OF MONOTOMHXE. 



a. Head slightly prolonged behind the eyes, then suddenly narrowed. 

 6. Process of abdomen between the hind coxae broad, feebly rounded in 



front. 



c. Terminal joint of antennae suddenly broader, joint nine not wider 



than eight. I. MONOTOMA. 



cc. Last two joints of antennae enlarged, ninth joint not as wide as 



the tenth; punctures of elytra in rows. HESPEROB^NUS. 



&&. Process of abdomen between the hind coxae triangular, acute ; ninth 



joint of antennae as wide as the tenth ; elytral punctures in rows. 



EUROPS. 



aa. Head parallel behind the eyes, not at all narrowed ; last joint of an- 

 tenna? suddenly enlarged, ninth not wider than eighth. 



II. BACTBIDIUM. 



I. MONOTOMA Herbst. 1703. (Gr., " one + cut.") 



In addition to the distinctly larger terminal joint of antennce, 

 the members of this genus have the head and thorax usually densely 

 punctured and the elytra with rows of punctures, each bearing a 

 short hair. The surface has a tendency to become coated with for- 

 eign matter, which adheres to the minute hairs and renders the 

 sculpture difficult to study. Of the nine species known from the 

 United States five have been taken in the State, while two others 

 perhaps occur. 



KEY TO INDIANA SPECIES OF MONOTOMA. 



a. Antennae slender, joints 4 to 9 longer than wide. PRODUCTA. 



aa. Antennae stouter, joints 4 to 9 bead-like or subrnoniliforin. 



b. Metasternum densely punctured at middle and sides ; thorax densely 



punctured. 



c. Head with a rather deep oblique impression on each side of vertex. 



1279. PICIPES. 

 cc. Head regularly convex, vertex not impressed. 



d. Thorax longer than wide. 1280. FULVIPES. 



dd. Thorax nearly square, or even slightly wider than long. 



e. Thorax with four rather deep impressions. QUADRIFOVEOLATA. 

 ee. Thorax at most with two feeble impressions near base. 



