ECOLOGY OF ISLE ROY ALE. 185 



8. Location of dominance and great abundance of individuals. 



9. Direction indicated by biogeographical or ecological affinities. 



10. Location of least dependence upon a restricted habitat, except 

 humid types in arid regions, and analogous cases. 



11. Location (when both a center of origin and dispersal) of maxi- 

 mum ecological differentiation in habits, habitats, food, etc. "Adap- 

 tive radiation," in part, of Osborn, 



By various combinations many additional criteria may be produced. 

 By sorting into groups most of the above criteria will readily fall into 

 either a taxonomic or ecologic class. But it will readily be seen that 

 no sharp distinction can be drawn between the two groups; and fur- 

 ther, no particular advantage is gained by such a classification. 



The neceBsarily condensed character of such formulations makes 

 further expansion and discussion desirable, but certain criteria are 

 so well known and easily understood that their discussion is not nec- 

 essary as in the case of No's. 1, 2 and 4; the remainder will be briefly 

 considered. 



3. Maximum size. This should be expected to apply to^ the larger 

 taxonomic units as well as to the smaller ones. In certain families, 

 genera, etc., there can be no question but that this criterion has great 

 value, although it might not apply to allied groups. The broader out- 

 lines of the relationship must be borne in mind and should not out- 

 weigh exceptional cases. This relation of large size and centers of 

 origin seems to be supported in part, by Murray's (70, pp. 7-8) pri- 

 mary strains of beetle descent. Two of the three strains, the Indo- 

 African and the Brazilian centers, contain the largest beetles. But 

 this entire subject needs critical study before its value and limitations 

 can be fully understood. 



5.i Seasonal distribution. Although familiar with this criterion, 

 it was, by an oversight, omitted from my former list of criteria. The 

 northern affinities of the vernal flora have long been known. - My atten- 

 tion to this oversight was called by my friend, Mr. A. B. Wolcott. 

 Recently Ulke ('02, p. 3) formulated this, in part, for beetles.. But it 

 should perhaps be extended to include montane forms also, as the ver- 

 nal fauna of the mountains may be expected to extend their breeding 

 range downwai'd, where they will appear as vernal forms at lower alti- 

 tudes. At the same time the fauna at lower altitudes might tend to 

 spread up the mountains where they would occur at the height of the 

 summer season. I do not know that this subject has been investigated. 



The late fall feeding habits and the lack of ability to resist low 

 temperature on the part of certain species which are extending their 

 range, may be indicative as to their direction of origin. Many plant 

 feeding insects, acclimated to northern localities, tend to cease feed- 

 ing some time before the fall frosts and are thus better able to resist 

 low temperatures (cf. Bachmetjew, '99, Zeit. wiss. Zool., 46, p. 600) 

 than those which feed late and are ^ell fed. Chittenden ('01, p. 74) has 

 recognized this general tendency, but has not correlated it with Bach- 

 irietjew's results. 



It is highly probable that there are many other seasonal pheno- 

 mena which indicate, in a general but more or less definite manner, the 

 direction of origin. 



