AMERICAN COLEOPTERA. 99 



SYNOPSIS OF AMBLYCHILA. 



Length, 30 mm. at least ; color, brownish ; surface of elytra, rugulose and irregu- 

 larly punctate ; apex of elytra, very coarsely punctured, elytra with 

 three cariuse cyliiKlriforinis- 



Length. 28 mm. ; color, deep black ; surface of elytra, smooth and regularly punc- 

 tate; apex of elytra, with punctures scarcely visible, elytra with three 

 carinse. Piccoloiniuii. 



Length, 2r> mm. ; color, deep black ; surface of elytra smooth and regularly punc- 

 tate ; apex of elytra, with punctures scarcely visible; elytra with one 

 carina Baron i . 



O.IIU^ Esch. 



Contains several species which, except Dejeani, are very similar. 

 All are confined to the Pacific Slope, ranging from Vancouver Island 

 southward to Santa Barbara, Cal., and eastward as far as Montana. 

 In habits nocturnal, the.se insects are said by Schanpp to be easily 

 baited by placing finely chopped meat under pieces of board, whei-e 

 they may be found the following day. The sexes are separated by 

 the anterior tarsi and last ventral .segment, viz. : 



(? . — Three joints of anterior tarsi dilated and spongy pubescent 

 beneath ; last ventral segment deeply emarginate at middle. 



9 .—Anterior tarsi simple; last ventral segment oval at tip and 

 entire. 



The species of Omus divide readily into two groups, one containing 

 a single species, Dejeani, distinguished by its large size and conspicu- 

 ous fovese ; the other containing many species of similar size and ap- 

 pearance, all smaller than Dejeani and all without its con.spicuous 

 foveje. They differ, however, in the sculpture of the thorax and 

 elytra, in outline and in locality, each form being confined to its 

 own particular territory. The differences in thoracic sculpture may 

 be reduced to four principal forms, i. e. 



Deeply wrinkled all over as in cnlifornicas. 

 Less deeply wrinkled all over as in Lecontei. 



Wrinkled at the sides, less deeply within and with a space in the centre free 

 from wrinkles as in Audouinii. 



Smooth without wrinkles as in Isevis. 



The differences in elytral sculpture might be used to further sub- 

 divide, but have so far been used only in the case of ambignns where 

 the elytra are as smooth as in kevis though the thorax resembles 

 Audouinii. 



The differences in locality being difficult to appreciate without a 



TKANS. AM. ENT. SOC, XXVIII. MARCH, 1902. 



