IV. 



CLASSIFICATION— A PRELIMINARY ARRANGEMENT OF THE 

 CANADIAN BARK-BEETLES. 



Introductory. 



The genera of the Ipidse have been arranged into tribes and subfamilies 

 in so many different ways that now a tribal or subfamily name is indefinite 

 unless followed by the name of the author. The four latest arrangements of 

 the groups have been advanced by Hagedorn, Nusslin, Reitter, and Hopkins. 

 Each differs radically from any of the others. The last, by Hopkins, representing 

 an extensive study of world species, is an exceedingly valuable contribution; 

 but there are sections of his arrangement with which I am as yet unable to agree. 

 His family "Scolytidm" seems to me only a subfamily; his subfamily "Crypha- 

 linw" to comprise two distinct and widely separated groups of genera; both the 

 "Corthylinoe" and the "Phloeotrihince" to group together genera that seem inipos- 

 sible in subfamilies of that extent, and Dendrodonus seems to me very widely 

 separated from Crypturgus and Dolurgus. 



A final acceptable arrangement of the Ipidae can be made, I believe, only 

 after a more complete study of the external and internal characters of world 

 species, an exhaustive study of the larvae, and a close comparison of habits. 

 It is of the greatest importance to study many individuals of each species, 

 particularly in groups such as Trypodendron and Dryoccetes, in which the species 

 are notably variable. A study of scores or preferably of hundreds of individuals 

 of each variable species, representing different localities, forms a basis for definite 

 conclusions; the examination of a few specimens rarely even suggests the limits 

 of variation. Tribal and even subfamily names are usually of minor importance, 

 often a matter of personal preference, and very largely a nuisance. The relation- 

 ships of the genera are usually indicated clearly enough by the grouping in the 

 generic keys. The keys which follow are preliminary and far from perfect; 

 they attempt a workable arrangement of the genera and Canadian species for 

 the use of students and foresters. Many of the doubtful points will be settled 

 eventually only by biologic studies. Internal characters have been included in 

 the keys but rarely, although they have been utilized extensively as checks. 

 Keys based upon the internal characters of such small insects are obviously 

 quite useless to the average worker, and in so far as this family is concerned 

 these internal characters seem usually to be no more reliable for phylogenetic 

 studies than those of the exterior. 



In the present paper the four leading groups of the Canadian Ipidos are 

 recognized as subfamilies; the Eccoptogasterince, the Hylesinince, the MicracincB, 

 and the Ipince. 



The keys to the species include the species known to occur in Canada and 

 those of the northern part of the United States in so far as they are represented 

 in literature and in our collection. In a few genera, such as Ips and Pityoph- 

 thorus, most of the North American species are included; but, in general, no 

 attempt has been made to cover those genera peculiar to the southern and 

 southwestern States. For instance, Hypothenemus and Stephanoderes, including 

 many southern species, are not represented in Canada and are therefore dis- 

 regarded. The Canadian species and others of special interest are treated 

 briefly in the catalogue. 



36198— 3i 



