COLORATION AFFECTED BY THE ENVIRONMENT. 47 



in some climatic or other condition, to produce similar 

 forms. 



There is a butterfly common in certain parts of the Ar- 

 gentine, which Dr. Seitz at first mistook for the European 

 Vanessa (Arascknia) levana, so closely does it resemble that 

 butterfly in colour, in the notching of the wings, and in other 

 ways. Moreover, there is a variety of this form which is in 

 the same way exceedingly like the form prorsa. A closer 

 examination of the insect showed that it did not belong to this 

 species at all, or even to the same genus ; it is a member of 

 another genus, Phyciodes. "If," says Dr. Seitz, "these were 

 found in our country, no one would doubt that this was a case 

 of mimicry as perfect as any which exists." It might be 

 suggested that it is a case of mimicry, but the mimicking and 

 mimicked forms have each gone their own way, one migrating 

 to one country and one to another ; they might possibly at one 

 time have both lived in North America, and later on separated, 

 one going south, and the other east, crossing over into Asia 

 by way of Behring's Strait. Such an explanation would be, 

 as Dr. Seitz points out, entirely contrary to what is known of 

 the distribution of these insects; for the genus Araschnia is 

 absolutely confined to the Old World, and Phyciodes to the 

 New World. 



We see here a particular type recurring in regions widely 

 separated, which may be reasonably supposed to be due to 

 similar environmental conditions. 



The resemblance between the Danaidaj, Acra^idre, Heliconidrc, 

 and Pieridie of South America may be mentioned here ; they 

 will be treated of in the chapter relating to mimicry; there 

 is also a Satyrid in which the wings have partially lost their 

 scaling, and there are other examples among South American 

 lepidoptera of the same transparency in the wings. /C\C A / 



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