LETTER OF TRANSMITTAL 



United States Department of Agriculture, 



Bureau or 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. 



Eespectfully, L. O. Howard, 



Chief of Bureau. 



Hon. James Wilson, 



Secretary of Agriculture. 



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