166 MICHIGAN SURVEY, 1908. 



the present fauna any special connection with that of the high regions to the 

 far South — the Andes. In order to arrive at just conclusions, it will be need- 

 ful to consider these points in some further detail. 



"Alpine Insects of the Andes. The recently-published 'Supplementary Ap- 

 pendix' to Mr. Whymper's work on his travels amongst the Andes of Ecuador, 

 containing an account of his captures, includes some very valuable 'information 

 about the insects of high altitudes in that country. The late Mr. H. W. Bates 

 has written the introduction, in which the following passages occur: 



" 'If there had been any distinct element of a North Temperate or South Tem- 

 perate Coleopterous Fauna on the Ecuadorian Andes the collections he made, 

 inexhaustive though they may be, would have shown some traces of it; but 

 there are none. A few genera belonging to temperate latitudes, though not 

 found in the tropical lowlands, do indeed occur, but they are forms of almost 

 world-wide distribution in similar climates, and there is no representative of 

 the numerous characteristic and common genera of the North or South. Even 

 the Northern genera, more or less abundantly found on the Mexican highlands, 

 are absent. 



" 'One feature of the fauna is of great interest. It is the occurrence of apterous 

 species of genera which at lower levels are always winged. 



"'It seems to me a fair deduction from the facts here set forth that no distinct 

 traces of a migration during the lifetime of existing species, from North to 

 South, or vice versa, along the Andes, have as yet been discovered, or are now 

 likely to be discovered.' 



"Going through the list of insects taken at high altitudes in Ecuador, the 

 following points may be noted. There are four new species of Pterosticfius 

 from 12,000 feet upwards, but they represent a, new subgenus. There is not a 

 single Amara or Harpalus. pp. 317-318. 



"The Glacial Epoch. It can readily be imagined that such a state of affairs 

 [Prestwick's account of the Amer. Ice Age] would lead to the destruction of 

 a large part of the fauna, the remainder either surviving along the northwest 

 coast-line, or going southward to the Gulf States and Mexico. The eastern 

 fauna, with wlilch we are not now particularly concerned, would largely sur- 

 vive, owing to there being a considerable area of unglaciated territory avail- 

 able. This, indeed, has been the case. The Californian fauna would survive 

 in part to the north, and also in lower California and the western coast region 

 of Mexico. But the fauna of the central region would be almost annihilated, 

 because the warm winds being cut off by the coast ranges, the country would 

 become extremely cold, even far down into the higher lands of Mexico. The 

 airid region where not actually glaciated would be a frozen desert, and the 

 migration of the fauna southward would be far from easy. 



"In the eastern province the species of the moist Northern States would find 

 little difficulty in migrating southward into the equally moist Southern States. 

 The isotherms would shift southward over moderately uniform country. In 

 the centrc'J region, however, this would not be the case. There is no place 

 available to the South, except the moister coast line, and the interior uplandSi 

 which latter were undoubtedly glaciated. The great plains between the Rocky 

 Mountains and the Mississippi would have made an impassable barrier for most 

 species, preventing migration in that direction. 



"But, it may be urged, at some point to the southward the mountains or 

 central uplands would cease to be glaciated, and why should not migration take 

 place into the neotropical region. That it did not take place at all events 

 Ijeyond the Isthmus, is evidenced by the facts above quoted from Mr. Whymper's 

 'Appendix;' and the reason of this no doubt is, that the isthmus itself was 

 submerged, and all connection between North and South America cut off. This 

 question of the submergence of the Isthmus of Panama hEis been fully, dis- 

 cussed by various naturalists, and need not be enlarged upon here. 



"It is impossible in the present paper to give more thiOi this bai-e outline 

 of the subject, but I believe the conclusion is justified, that the central region 

 fauna was practically stamped out during the glacial epoch; and that the 

 present fauna is derived from the boreal faunae which survived to the east 

 and to the west, and the southern fauna which survived in Mexico. This view 

 seems to be supported by a consideration of the present distribution of species, 

 as well as by geological evidence, pp. 319-320. 



"Post-Q-lacial Developments. Excepting the remnants of the ancient fauna, 



