TRANSACTIONS 



OF THE 



AMERICAN ENTOMOLOGICAL SOCIETY. 



VOIvUN/[K XVII. 



The species of HETEROCERUS of Boreal America. 



BY GEORGE H. HORN, M. D. 



AVith most collectors Heterocerus does not seem to have been held 

 in much regard. The species have been looked upon as almost in- 

 separable, and the small amount of literature devoted to them has 

 been practically inaccessible to nearly all. To myself they had 

 been equally unattractive until the large material which had accu- 

 mulated in a quarter of a century required to be dealt with and 

 properly arranged, a task of no small difficulty in a mass of several 

 hundreds from all parts of our country in every style of cabinet 

 preparation. 



In a work of this character, after the specimens have been uni- 

 formly mounted and prepared for study, the first essential step is the 

 separation of the sexes. This is not a matter of much difficulty, 

 although the males are far less numerous than the females. In the 

 males the head is larger and more prominent, the mandibles more 

 slender and projecting, the labrum longer, and in one group pro- 

 longed at middle in a process of varying length according to the 

 species. The clypeus is also retuse to a varying degree, and is espe- 

 cially well marked in the species with a prolonged labrum. The 

 thorax is at least as broad as the elytra, sometimes slightly broader, 

 and not gradually narrowed to the front as in the female. 



TKANS. AM. ENT. sec. XVII. (1) .JANUARY, 1890. 



