182 MICHIGAN SURVEY, 1908. 



2. That the Stikine Canon fauna is more closely allied to that of the North and 

 Bast than is that of the coast, and about the same as is that of Glenora. 



3. That the chief relations of all three are in the direction of Lake Superior: 

 with larger lists this affinity might turn to the Rocky Mountains, especially in 

 the case of Glenora. 



Regarding the affinities of the faunae of the Coast, the Stikine Canon and 

 Glenora among themselves we find: 



4. That one-sixth of the CoaSt species extend up to the Canon while only one- 

 thirtieth reach Glenora. 



5. That the last-named fauna is much more closely allied to that of the Canon 

 that to that of the Coast; nearly one-fourth of the Glenora species are found also 

 at the Canon while only about one-eleventh extend to the Coast. 



6. That the fauna of Glenora is apparently less related to that of the Coast 

 than to that of the interior or the East. 



"Reference to the accompanying mai)s will throw some light on the problems 

 here suggested. Glenora is on the inside of the great Coast Ranges while the 

 Little Canon is regarded by Dr. Dawson as marking the head of the old salt-water 

 inlet that has been silted up. This would account for much in the distribution of 

 the species in question. The climate of the country above the Canon is also much 

 dryer and with greater extremes of heat and cold than on the Coast. Aside from 

 the influence of the barrier of the Coast Mountains interposed between faunae 

 which might tend to intermingle, the change of plants consequent upon difference 

 in climate on opposite sides must also have its effect on the insects dependent 

 on vegetation for food." pp. 232-233. 



1905. p. 46. 



"My proposed explanation, correlating the briefly outlined geological history with 

 the facts offered as to the distribution of the insects [shore insects of the Great 

 Basin], may be summarized as follows: 



1. The shore beetles under consideration are confined to the Great Basin or its 

 immediate borders, and have, in general, no allies in other districts from which 

 they could have been recently developed. This in itself is strong presumptive 

 evidence that they are endemic, not immigrants. 



2. Within the Basin, recent conditions are such that the present distribution 

 cannot possibly be a matter of modern origin. The small lakes now remaining 

 in the Basin are separated by great tracts of arid desert, impassable to beetles 

 depending on a moist soil for their development and food supply. The nature of 

 these insects is such that they cannot be carried long distances, as eggs or larvae, 

 on the feet of birds or other animals. 



3. Ancient conditions, as shown by the geological history through the Pleisto^ 

 cene, were favorable to the diffusion of shore-loving insects through the Basin, 

 because of the much greater extension of the lakes in those times. 



4. The Insect most thoroughly studied, Cicindela echo, is entirely confined, in 

 its present range, to the neighborhood of lakes, from which their size and the 

 presence of nearby springs, may be presumed to have lasted in some form from 

 a remote period — even through times of severe drought. Other littoral forms 

 follow the, same general law, though some of them are less sensitive to local con- 

 ditions. 



"From these facts, I think we can come to but one conclusion— the beetles under 

 consideration are types that have inhabited the Basin during the Pleistocene Umes 

 V. hen the shores of the great lakes stretched over hundreds of miles of what are 

 now desert sands. As the lakes shrunk during times of drought, the insects fol- 

 lowed the retreating beaches. Those which attached themselves to bodies of 

 sufficient size or permanence were able to sustain their specific existence, while 

 such as were dwelling on the edges of pools of a transient nature were extermin- 

 ated altogether. Thus we have the phenomenon of discontinuous distribution, 

 presented not by one species alone but by an entire assemblage." p. 46. Cf 

 Wickham, 1904. 



2. Comments on the Preceding Generalisations and on the Literature 

 of Geographic Distribution. The American authors who have given 

 special attention to the study of the geographic distribution of our 

 beetle fauna are few in number, but they are very representative men. 

 First and foremost is Dr. J. L. LeConte, the most I'emarkable and 



