HOPKINS HOST-SELECTION PRINCIPLE AS RELATED 

 TO CERTAIN CERAMBYCID BEETLES 



By F. C. Craighead 



Specialist in Forest Entomology, Bureau of Entomology, United States Department of 



Agriculture 



INTRODUCTION 



In connection with the reported dying of lodgepole pine (Pinus con- 

 torta Loud.) over extensive areas in northeastern Oregon caused by the 

 mountain pine beetle {Dendroctonus moniicolae Hopk.) and the threat- 

 ened invasion by this beetle of the adjacent areas of yellow pine {Pinus 

 ponderosa Laws.), detailed investigations were made by the Bureau of 

 Entomology under the direction of Dr. A. D. Hopkins. Manuscript 

 reports of these investigations, submitted in the summer of 19 lo, showed 

 that the infestation by the beetle in the lodgepole pine was so extensive 

 that there was no hope of controlling it, but that the comparatively small 

 amount of infestation in the valuable stands of yellow pine was such as 

 to warrant the undertaking of control, provided the beetle did not 

 migrate from the lodgepole pine to the yellow pine. 



In a letter from Dr. A. D. Hopkins under date of July 30, 19 10, relating 

 to a manuscript report of Mr. H. E. Burke, the following statement 

 occurs which appears to be the first written reference to the host-selection 

 principle : 



The more I consider the various features of the problem, the more I am convinced 

 that it is entirely practicable to protect the yellow pine, even if we leave all but the 

 immediately adjacent lodgepole pine to take care of itself. This is based on my 

 belief that the majority of the broods of the beetles which have been breeding in the 

 lodgepole will continue to confine their attack to that species, and gradually diminish 

 with the reduced supply and their increased struggle to adapt themselves to the 

 yellow pine. I may be wrong in this, but it is a matter worthy of careful considera- 

 tion. Remember, that in all these years, there has been no marked or general migra- 

 tion of beetles from lodgepole to the yellow pine. Therefore, it appears that the 

 broods which are most dangerous to the yellow pine are those which have been breed- 

 ing in it, and that these are the broods we will have to deal with mainly in our efforts 

 to protect the best bodies of yellow pine. 



The control operations that were carried on during the following year, 

 191 1, were confined mainly to the yellow pine area. In manuscript 

 reports by Messrs. W. D. Edmonston and George Hofer on a special 

 examination of the yellow pine and lodgepole pine areas in the summer 

 and fall of 1913, it is stated by Edmonston: 



In 1912 the examination of the areas on which insect control work was carried on 

 during April, May, and June, 191 1, showed an average reduction of the infestation 

 on the entire area, 76,430 acres, of close to 85 per cent. 



Journal of Agricultural Research Vol. XXII, No. 4 



Washington, D. C. Oct. 22, 1921 



aac (1S9) Key No. K-ioa 



