256 STUDIES, SCIENTIFIC AND SOCIAL chap. 



winged and apterous species in the same genus, as well 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 

 presumption, if not almost a certainty, that all apterous 

 varieties, species, or groups, have been derived from 

 winged ancestors, — comparatively 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 transmission across the sea, we 

 should expect them to be wholly absent, or, if there are 

 any exceptions, we should expecfc to be able to detect some 

 special circumstances which might favour their trans- 

 mission. A careful examination of Lacordaire's Genera, 

 and of some works on European Coleoptera, has furnished 

 me with the following list of genera which are wholly 

 apterous, and which abound in South Europe and North 

 Africa. 



Carabus possesses about 80 species in these regions ; but 

 is wholly absent from Madeira. 



Thorictus has 10 South European species, and one 

 representative in Madeira, which is an ants'-nest species. 



Rhizotrogus (Melolonthidae), 27 species in Sicily and 

 Algeria, the very countries to which the Madeiran fauna 

 is traced, yet it is wholly absent. 



Lampyris, Drilus and Troglops (Malacoderms), of which 

 the females are apterous, possess 27 South European and 

 North African species;, none in Madeira. 



