74 



country), is permanently smaller in Porto Santo ttan it 

 is on the larger, more luxuriant and varied, and there- 

 fore more protected, island of Madeira proper. And, as 

 regards the Ptini of that group, so completely are some 

 of them "affected by isolation, and by exposure to a 

 perpetually stormy atmosphere, that they do not attain 

 half the bulk on many of the adjacent rocks that they 

 do ia the more sheltered districts of the central mass ; 

 and so marvellously is this verified in a particular 

 instance, that I have but little doubt that five or sis 

 species (so called) might have been recorded out of one, 

 had only a few stray specimens been brought home for 

 identification, without any regard having been paid to 

 the respective circumstances under which they were 

 found*." That "one," Protean, representative is the 



theless, recollecting how easy of transport the larvse and pupse of 

 Lepidoptera necessarily are (of which we have the plainest assu- 

 rance in the almost certain introduction of the Pontia BrassiccB, 

 Sphinx Convolvuli, Acherontia Atropos, &c. into those islands), 

 especially in a region which for more than a century has been 

 receiving a constant supply of vegetables and ornamental plants 

 from western Europe ; I am induced to believe that the appearance 

 of the Atalanta is a comparatively recent one, whilst that of the 

 Callirhoe (which, unhke the typical Red Admiral, has naturalized 

 itself in nearly all portions of the group) must be referred to the 

 remote period when migrations over a long-lost continuous land 

 were in regular operation. The slowness of the change, in external 

 aspect, which the isolation of insects from geological causes would 

 seem to bring about (and which follows, as a corollary, if the above 

 conclusion be true), I propose to discuss in a subsequent chapter of 

 this work. 



* Insecta Maderensia, p. 260. 



