Iviii 



tinuity, how are we to explain the absence of extensive genera 

 very abundant in South Europe, and, from their being apterous, 

 specially adapted to the peculiarities of Madeira ? Such are 

 Carahus, Lanqyi/ris, Pimelia, Akis, and man}^ others. But these 

 facts are all consistent with the theor}^ of introduction across the 

 sea. Apterous groups, however abundant on the continent, 

 should, as a rule, be absent; and I find that almost all the 

 European apterous genera are wanting, and among the few 

 exceptions there are some whose presence is easily explained and 

 really prove the rule. We must remember, however, that the 

 apterous condition, except in those cases where it is charac- 

 teristic of an extensive group, is one of little stability or im- 

 portance. There are species which are sometimes apterous and 

 sometimes winged, and we may therefore be sure, that if any 

 advantage was to be derived by either condition over the other, 

 natural selection would very rapidly render it constant by the 

 repeated survival of the favoured individuals. This is illustrated 

 by the fact that we have winged and apterous species in the same 

 genus, as w^ell as winged and apterous genera in the same family. 

 The Coleopterous Order being essentially winged, and the vast 

 majority of its members being capable of flight, it is a presump- 

 tion, if not almost a certainty, that all apterous varieties, species, 

 or groups, have been derived from winged ancestors, — com- 

 paratively recently in the case of the former, and at a more remote 

 epoch as the character becomes more constant and attached to 

 groups of higher classificational value. 



Taking these principles as our guide, let us examine more 

 closely the facts presented by the Madeiran Coleoptera, and their 

 bearing on the rival theories as to their mode of introduction. 



There are a large number of European beetles belonging to 

 very varied genera and families which are apterous, and a large 

 proportion of these inhabit the South of Europe and North 

 Africa. Now, on the theory of land-connection, there should be 

 no marked absence of these groups ; on the contrary, apterous 

 forms being especially adapted to Madeira, we should expect 

 them to predominate. But, on the opposing theory of trans- 

 mission across the sea, we should expect them to be wholly 

 absent, or, if there are any exceptions, we should expect to be able 

 to detect some special circumstances which might favour their 

 transmission. A careful examination of Lacordaire's ' Genera,' 



