NORTH AMERICAN COLEOPTERA. 



27 



Notes on the species of Dendroctouus of Boreal America. 



BY W. G. DIETZ, M. D. 



A study of my material of this genus, chiefly undertaken for the 

 purpose of i)lacing some doubtful forms, has led to the discovery of 

 characters definite and easily recognizable, which thus far have been 

 overlooked. Further investigation, covering all the material and 

 representing all the species hitherto recognized, contained in the col- 

 lections of Dr. Horn, Mr. H. Ulke and Dr. J. Hamilton, has con- 

 firmed these and made the separation and identification of the species 

 at once positive and easy of attainment. The anterior margin of 

 the rostrum, which for convenience, I shall here designate as epis- 

 toma presents each side of the middle an incisure or cleft, which 

 divides this part into three segments. The middle segment is slightly 

 retracted and somewhat overlaps the lateral segments ; it varies so 

 in form, length and width, as to be almost characteristic of each 

 species, and when taken in connection with characters afforded by 

 the structure of the antenme, determines the exact limits of each 

 species. Without going into a minute description of the characters 

 spoken of, I deem it preferable to illustrate them by the accompa- 

 nying figures, which I hope will convey a more accurate idea than 

 description could do and which will be referred to in the following 



pages. 



Color is of no value whatever in distinguishing the species, and 

 even sculpture, of such great value in the differentiation of species 

 elsewhere, plays but a very subordinate part here. The hairy vesti- 

 ture, while fairly constant for each species, has only a relative value 

 difficult of expression. 



Although sought for assiduously, I have failed to discover any 

 character positively indicating the sex. Generally speaking, the 

 % % are more slender and more shining, the thoracic punctures and 

 elytral asperities less pronounced and the latter sometimes replaced 

 by punctures on the declivity. 



After these preliminary remarks I offer the following analytical 

 table for the identification of our species. It will be seen that D. 



