ECOLOGY OF ISLE ROYALE. 183 



'•exceptional" of American entomologists. A man who, liad lie devoted 

 himself to subjects of more general interest than insects or to more 

 general problems would, in all probability, have been generally re- 

 cognized as one of the greatest of American naturalists. Other students 

 v/ho have devoted much attention to distribution, although none have 

 liiven as much attention to the general principles of the problem as did Le- 

 Conte, are: Schwarz, Hubbard, Hamilton, Wickham and Cockerell. 

 Then there are several autliors of local lists which must furnish the 

 basis for comparisons, but only in a few cases do the authors of these 

 local lists attempt to discuss the general char act cri-stics of their fauna 

 or compare them with those of other localities. This is certainly an 

 unfortunate omission, particularly so as, in general, the authors of 

 such lists should be the most competent to discuss the main features 

 of their fauna. Of the various local lists, two are to be particularly 

 commended for the ecological notes which they contain: those by 

 !-^(hwarz in Ulke's Washington list, and those by Hamilton, in the Pitts- 

 burg list. It is through the ecological influences upon distribution that we 

 must expect the greatest advances in the future study of distribution. 

 In this connection there should be mentioned the studies by Webster 

 on the routes of dispersion of certain species, particularly those of 

 economic importance. A very useful bibliogi'aphy of local lists of beetles 

 has been published by Hamilton and Henshaw ('91-'92), and still other 

 recent local lists will be found in the bibliography accompanying this 

 paper, although no attempt at completeness is made. 



Limited time has prevented a detailed discussion- of the qviotations 

 as originally intended, but in their present form they are much more 

 accessible than when scattered. 



V. The Present Centers of Dispersal of the Beetle Fauna. 



The general characteristics of the Isle Eoyale beetle fauna can only 

 be appreciated through a comparison with other areas, particularly^ 

 with those of boreal regions and the remainder of the North American 

 continent. Only the major features can here be outlined. It has been 

 tliought desirable to consider the subjects from the standpoint of centers 

 of dispersal, rather than from the current taxonomic standpoint because 

 of the emphasis thus put upon the genetic side of distribution and its 

 ecological relations. 



In a former paper, (Biol. Bull., 1902, 9, p. 122) the writer listed 

 certain criteria which may be used to determine biotic centers of dis- 

 persal and centers of origin. As is well known, centers of origin and 

 centers of dispersal do not necessarily coincide, although all established 

 centers of origin must be centers of dispersal. Centei's of origin are 

 very often difficult or impossible to determine with the present state 

 of knowledge; and many are likely to remain so indefinitely. Then 

 there is the possibility, or even probability, that some forms have origi- 

 nated at more than one place, and independently. Ttis certainly com- 

 plicates the subject of origins, increases the importance of determin- 

 ing themi, and means that this method must be repeated in such cases, 

 but not that such determinations are impossible. Centers of origin, 

 either single or multiple, at once become centers of dispersal, and 

 by means of dispersal new centers become established so that there 



