XII THE COLEOPTERA OF MADEIRA 263 



There is one other group of islands which seems well 

 adapted to offer a crucial test of the correctness of the 

 theory of land-connection. The Azores are more than 

 twice as far from Europe as the Madeiras, and, what is 

 of still more importance, they are cut off from it as well 

 as from the Madeiras by a broad belt of ocean of the 

 enormous depth of nearly 15,000 feet. We may feel pretty 

 confident, therefore, that if both groups have once been 

 united to the continent, the separation of the Azores is by 

 far the more ancient event ; and any theory which requires 

 the Azores to be the most recently separated must be 

 strongly supported by independent evidence to render such 

 an improbable supposition acceptable. If the Azores date 

 the origin of their insect population from a remote epoch 

 when they were connected with Europe, we should expect 

 to find that almost all the species have since become 

 modified, and that these islands would offer us a larger 

 proportion of highly specialised and ultra-indigenous 

 forms than Madeira itself. The exact contrary, however, 

 is the fact, for out of more than 200 species only about 

 sixteen are peculiar. Taking the geodephagous group, the 

 species of which, both Mr. Murray and Mr. Wollaston 

 believe, are least liable to be introduced by man, we find 

 that two only are pecuhar, while sixteen are European. 

 The Rh3^nchophora only equal the Geodephaga in number 

 of species, and seven of these are peculiar. Leaving out a 

 large number of species which have, there is little doubt, 

 been introduced through human agency, there remain 

 more than 100 species identical with those of Europe and 

 the Atlantic islands, while only fourteen are peculiar. 

 These facts imply that the insects, as a whole, have been 

 brought to the islands through natural causes, and that 

 the process is probably still going on. On looking to 

 Physical Maps for information, however, a difficulty appears; 

 for the ocean currents, as well as the prevalent regular 

 winds, are all from the westward, while only four of the 

 beetles are American, and these being all wood-borers have 

 no doubt been brought by the Gulf-stream or in some cases 

 havebeen introduced by man. Fortunately, however, we have 

 a means of getting over this difficulty ; for Mr. F. Du Cane 



