LETTER OF TRANSMITTAL. 



U. S. Department of Agriculture, 



Bureau of Entomology, 

 Washington, B. C, October 20, 1913. 

 Sir: I have the honor to transmit herewith a manuscript entitled 

 "American Black Flies or Buffalo Gnats," by J. R. Malloch, an 

 entomological assistant in this bureau. This paper deals with a 

 group of flies of considerable economic importance. As pests to man 

 and domestic animals certain species of the group have long attracted 

 attention in this country and elsewhere. Eecently additional inter- 

 est in these insects has been created hj the theory that certain species 

 transmit pellagra. This theory has not been proven and it is not 

 accepted by the great majority of investigators. Nevertheless the 

 importance of the buffalo gnats as pests to man and domestic animals 

 is so great that accurate information regarding the species which 

 exist in this country is highly desirable. This paper includes de- 

 scriptions of several species new to science and in other respects adds 

 very materially to our knowledge. I recommend the publication 

 of this manuscript as Technical Series No. 26 of the Bureau of 

 Entomolog}'. 



Respectfully, ' L. O. Howard, 



Entomologist and Chief of Bureau. 

 Hon, D. F. Houston, 



Secretary of Agriculture. 



