OF WASHINGTON. 6 



they are uncommon, though more than one has been found in a 

 single colony. He doubted whether, in view of the roving habits 

 of this species, a true queen really exists with them. 



Prof. Hopkins then read his paper entitled " Notes on the 

 Genus Dendroctonus," of which he has prepared the following 

 abstract for these minutes : 



SOME NOTES ON THE GENUS DENDROCTONUS. 

 By A. D. HOPKINS. 



(Author's Abstract.} 



Attention is called to the meagre knowledge of the Dendroc 

 tonus and the confusion due to the failure, heretofore, to recog 

 nize good specific and secondary sexual characters. The genus 

 is referred to as one of great economic interest on account of its 

 being represented by the most destructive enemies of coniferous 

 trees. 



Reference is made to the habits and distribution of the twelve 

 new species named and described, and three restored from 

 synonyms. The new species are named as follows: D. pini- 

 cida, D. arizonicus, D. monticolce, 1}. ponderosce, D. keeni, 

 D. fletcheri, D. piceceperda, D. dietzi, D. calif or nicus, 

 D. s/ws/ione, D. wickhami, D. borealis. Those restored are : 

 D. brevicomis Lee., D. punctatus Lee., and D. obesus Mann. 

 These new and restored names, added to those previously adopted 

 for the eight species described from this and other countries, 

 make a total of twenty-four species twenty-one in America 

 north of Mexico, two in Central America, and one in Europe. 



The species are divided by secondary sexual and other char 

 acters into two primary, two secondary, and six minor divisions. 



Results are given of a detailed study of the ratios of difference 

 in micrometer measurements of different parts of the prothorax, 

 which showed a gradual decrease in the ratios of the anterior 

 width, and the length, to the posterior width, from D.frontalis, 

 which represents the maximum, to D. borealis, which represents 

 the minimum of this line of variation through the genus. 



It was also found that the sum of the mean ratios (or per cent, 

 of differences) of the anterior width to the posterior width, and 

 the length to the posterior width in the different species, gave 

 numbers which expressed, or indicated, the relative value of this 

 composite character, thus determined, in the separation and 

 classification of the species into what appear to be the most 

 natural primary and minor divisions. 



The classification based upon the results obtained by the 

 " statistical method " were verified by the ordinary use of secon- 



