chap, x.] THE PAL^ARCTIC REGION. 213 



islands and also occurs in South Europe, but is always apterous. 

 It is however closely allied to another genus, Cryptorhynchus, 

 which is apterous in some species, winged in others. We may 

 therefore well suppose that the ancestors of A calks were once in 

 the same condition, and that some of the winged forms reached 

 Madeira, the genus having since become wholly apterous. 



We may look at this curious subject in another way. The 

 Coleoptera of Madeira may be divided into those which are 

 found also in Europe or the other islands, and those which are 

 peculiar to it. On the theory of introduction by accidental 

 immigration across the sea, the latter must be the more ancient, 

 since they have had time to become modified ; while the former 

 are comparatively recent, and their introduction may be supposed 

 to be now going on. The peculiar influence of Madeira in 

 aborting the wings should, therefore, have acted on the ancient 

 and changed forms much more powerfully than on the recent 

 and unchanged forms. On carefully comparing the two sets of 

 insects (omitting those which have almost certainly been 

 introduced by man) we find, that out of 263 species which 

 have a wide range, only 14 are apterous ; while the other class, 

 consisting of 393 species, has no less than 178 apterous ; or 

 about 5 per cent in the one case, and 45 per cent in the other. 1 

 On the theory of a land connection as the main agent in intro- 

 ducing the fauna, both groups must have been introduced at or 

 about the same time, and why one set should have lost their 

 wings and the other not, is quite inexplicable. 



TakiDg all these singular facts, in connection with the total 

 absence of all truly indigenous terrestrial mammalia and reptiles 

 from these islands — even from the extensive group of the Cana- 

 ries so comparatively near to the continent, we are forced to 

 reject the theory of a land connection as quite untenable ; and 

 this view becomes almost demonstrated by the case of the 

 Azores, which being so much further off, and surrounded by 

 such a vast expanse of deep ocean, could only have been con- 



1 The facts on which these statements rest, will be found more fully 

 detailed in the Author's Presidential Address to the Entomological Society 

 of London for the year 1871. 



