252 STUDIES, SCIENTIFIC AND SOCIAL chap. 



published, Mr. Godman relates that a white butterfly flew 

 on board a whaler coming from the south, at about 400 

 miles from the Azores : it was caught by the captain and 

 placed in a drawer, where it laid several eggs.^ Such 

 cases as these having been already recorded, we may be sure 

 that migrations to much greater distances are constantly 

 occurring, since we can hardly suppose the extreme cases 

 to be those which have first been observed. We have 

 therefore every reason to believe that, under favourable 

 conditions, almost any winged insect could traverse equal 

 distances. These considerations would lead us to the con- 

 clusion that a partial identity of species may exist in the 

 beetles of two countries separated by some hundreds of 

 miles of sea, without in any way necessitating the former 

 existence of a continuity of land between them. In the 

 case of the Atlantic islands, therefore, I see no reason to 

 believe that they owe their Coleoptera to a land-connection 

 with the continent, more especially when there is such 

 strong evidence against that view in the total absence of 

 all mammals and reptiles. Can we believe that the 

 forests of Madeira would be without a single native 

 rodent, or even a frog, if they owed their rich coleop- 

 terous and molluscous faunas to land-connection with 

 Europe ? 



The exhaustive researches of Mr. Wollaston in these 

 islands will, I believe, furnish, in the single order of Cole- 

 optera, ample materials for the elucidation of this very 

 interesting question. Although the Insecta Maderensia 

 has now been published more than forty-six years, the vast 

 store of facts which it contains bearing on the question of 

 geographical distribution, and especially on that of insular 

 faunas, has never been fully appreciated ; and as neither 

 Mr. Murray nor later writers have grappled with these 

 facts as a whole, or attempted to show how they are com- 

 patible with their theory, I think it advisable to give a 

 somewhat detailed analysis of them, pointing out what I 

 conceive to be their true bearing on the problem of the 

 mode of distribution of beetles and the origin of insular 

 faunas. My interpretation of the evidence may be erro- 



^ Other cases are given in my Dartoinism, p. 359. 



