No. 593] SHORTER ARTICLES AND DISCUSSION 



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the remarkable "mimicry-rings" of South America that have 

 been so interestingly discussed by Punnett. In each of several 

 great regions of that continent a characteristic color pattern is 

 exhibited by unrelated species belonging to different genera and 

 even to different families. The color pattern followed in Central 

 America differs slightly from that adopted by members of the 

 same genera in eastern Brazil, a single genus of Pierids only 

 dropping out of the ring in the latter region. In western Brazil 

 and the upper Amazons the pattern is somewhat more mottled 

 and the ground color darker, but the same genera are represented 

 almost without exception. Finally, in Ecuador, Peru and Bolivia 

 the pattern common to the different genera is still darker and 

 greatly simplified. The Pierids here have left the ring, and a 

 Papilio, an Acrcea and two species of the Satyrid genus Pedali- 

 odes have entered it. The point to be emphasized, however, is 

 that the same genera, e. g., Heliconius, Mechanitis, have repre- 

 sentatives in each local color group. 



Let us now assume, with Punnett, that a set of similar or iden- 

 tical color factors is common to all the structurally diverse mem- 

 bers of each ring, and add the further hypothesis that the color 

 pattern resulting from these particular factors is to a large ex- 

 tent influenced by climatic conditions, as in seasonally poly- 

 morphic insects. It then follows that certain members of a 

 "ring" migrating from the tropical climate of Brazil to the 

 temperate zone farther south, even before they should become 

 changed genotypieally, would react to the new environment by 

 assuming a new color pattern such as that now characteristic of 

 the south temperate zone. If the genotype were identical 

 throughout the migrating group and a single member of the 

 group should so react, all naturally would respond in the same 

 manner. Seasonal polymorphism thus may furnish an addi- 

 tional clue to the explanation of this most interesting case of 

 convergence and parallelism in evolution. 



This discussion leads to the conclusion that seasonal variations 

 have a hereditary basis more sensitive than that of other color 

 characters to temperature and other climatic conditions. A sea- 

 sonal variation that is constant in its recurrence is transmissible. 

 Its hereditary basis invariably reacts in a certain definite way to 

 a certain narrow range of external conditions, whereas the hered- 

 itary basis of other characters, e. g., eye color in vertebrates, 



