LETTER OF TRANSMITTAL. 



United States Department or Agriculture, 



Bureau of Entomology, 

 Washington, D. C, May 3, 1912. 

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

 " The Principal Cactus Insects of the United States," prepared by 

 Messrs. W. D. Hunter and J. D. Mitchell, of this bureau, and the late 

 F. C. Pratt, who for many years was in the employ of the bureau. 



In the work of the Bureau of Plant Industry on the utilization of. 

 the prickly pear as a farm crop it became evident that insect injury 

 in plantings was of considerable importance. This observation was 

 made by Mr. David Griffiths. In 1907 he brought the matter to the 

 attention of the Bureau of Entomology and the investigation upon 

 which the present manuscript is based was begun. During the work 

 the bureau has profited by the close cooperation of Mr. Griffiths^ and 

 many of his observations are included in this report. 



I recommend that this manuscript be published as Bulletin No. 113 

 of the Bureau of Entomology. 



Respectfully, L. O. Howard, 



Chief of Bureau. 

 Hon. James Wilson, 



Secretary of Agriculture. 





