136 THE SCOLYTID BEETLES. 



Variations. The length varies from 6 to 7 mm., with the average 

 about 6.5 mm. The color ranges from uniform light red to brown in 

 young specimens, to uniform black in matured ones, it being exceed- 

 ingly rare to find examples with the pronotum darker than the elytra, 

 which is so characteristic in the three preceding species. The sculp- 

 ture and vestiture of the epistoma, front, pronotum, and elytra vary 

 as usual. The greatest variation is in the punctures of the pronotum 

 and in the presence and absence of the dorsal line; the presence or 

 absence of a frontal carina is also an important variation, and in some 

 examples the body is noticeably more elongate than in others. 



Distinctive characters. The characters which serve to distinguish 

 this species from the three preceding are the uniform black color of 

 the matured adults and the prevailingly less impressed elytral striae, 

 especially those of the lateral area, and also the prevailing slightly 

 more elongate form. Its host tree and distribution also serve as 

 distinguishing characters, except, perhaps, in the case of borealis, 

 which may be found in the Sitka spruce. 



Revisional notes. There can be little or no doubt that the material 

 under observation represents Mannerheim's species, whose varieties 

 a, b, and c were evidently immature specimens. D. similis Lee. is 

 to be referred to this, which fact was recognized by Le Conte in his 

 1868 paper, but the beetle was subsequently confused with the 

 species discussed in the present paper under D. pseudotsugx. D. obesus 

 is represented in the Le Conte collection by two specimens, one 

 specimen from Mannerheim's collection, labelled D. obesus (" Speci- 

 men 5" under D. rufipennis in 1900), and one specimen, the type 

 of D. similis. It is possible that " specimen 2" under D. rufipennis 

 is also D. obesus, but was not recognized by the writer when ex- 

 amined in 1900. Dietz, 1890, did not recognize or mention D. obesus, 

 and it was not found by the writer in the Horn collection or that of 

 the Academy of Natural Sciences. 



Pupa. In addition to the generic, divisional, and subdivisional 

 characters, the apices of the front and middle tibiae are smooth or 

 rarely with a single granule, abdominal tergites 2 to 6 with very 

 small pleural spines, 1 without dorsal but with small lateral spines, 

 and 2 to 6 with dorsal and lateral ones, 7 and 8 smooth, 9 with 

 prominent pleural spine as usual. Pupal type labeled "Hopk. U. S. 

 No. 4049a." 



The usual variation in minor details prevails, but the pupa of 

 this species is distinguished from that of the three preceding by the 

 more evident lateral spines of the first abdominal tergite and the 

 prevailing darker tips to the abdominal spines. 



Larva. In addition to the generic, divisional, subdivisional, and 

 sectional characters, the front has a faint transverse elevation dis- 





