LETTER OF TRANSMITTAL 



U. S. Department of Agriculture, 



Bureau of Entomology, 



Washington, D. C, March 16, 1909. 



Sir: I have the honor to transmit herewith manuscript of the first 

 part of a bulletin of the technical series to be entitled ''Contributions 

 toward a Monograph of the Scolytid Beetles." This family of beetles 

 includes some of the most important enemies of North American 

 forests, as well as of crude forest products, and therefore must demand 

 special attention in future systematic and economic investigations 

 by this Bureau and by forest entomologists connected with other 

 public institutions and private enterprises. It is necessary, as a foun- 

 dation for such work, that the heretofore-described species should be 

 accurately identified, that those new to science should be described, 

 and that this information, together with other systematic data 

 based on original research by this Bureau, .should be made available 

 in the form of contributions to a monograph. This work has been 

 undertaken by Doctor Hopkins, of this Bureau, and the greater 

 part of the collecting and working up of the material has been com- 

 pleted. Delay in pubUcation will be avoided, and it is believed 

 that the published results will be more useful in future systematic 

 and economic investigation if the results relating to groups of species 

 which have similar characters and characteristics and similar rela- 

 tions to given economic problems are pubUshed as parts of a bulletin" 

 rather than in one undivided publication. These technical parts 

 are to be supplemented in a like manner by parts of a bulletin of 

 the regular series, giving information of immediate practical impor- 

 tance to the forester and owners and managers of private forests. 



The first part of this bulletin is entitled "The Genus Dendroc- 

 tonus." It embodies the results of extensive systematic investiga- 

 tions of the genus, carried on by Doctor Hopkins during the past 

 seventeen years, and is of especial interest and importance from the 

 fact that it deals with a small group of beetles wliich are the most 

 destructive enemies of the principal coniferous forest trees of North 

 America. 



The discussions and illustrations relating to anatomical and tech- 

 nical details are necessary as a basis for the correct description. 



