

THE NEW EVOLUTION 



Amazon region and one from Ecuador, all of the 

 species of American Aristolochia swallowtails with 

 tails occur from Costa Rica northward, and from 

 temperate Brazil southward. All the very numerous 

 species in the region between Costa Rica and central 

 Brazil except for the two mentioned are wholly with- 

 out tails. Our common North American blue swal- 

 lowtail loses its tails in the southernmost portion of 

 its range. A number of Asiatic swallowtails gradu- 

 ally lose their tails toward the southeast, among the 

 islands of the Malayan archipelago. 



On the West Indian island of Jamaica there is a 

 marked tendency toward an increase of the black 

 markings in the local butterflies. 



On the island of New Guinea the local representa- 

 tives of wide-ranging butterflies are smaller than the 

 forms found elsewhere; the largest forms are those 

 which occur on the island of Amboina. 



In high mountain regions butterflies become ex- 

 tremely variable, varying from peak to peak, from 

 valley to valley, and frequently in different portions 

 of the same valley. This is most evident in the 

 Himalayas and the mountains to the northward, and 

 in the Andes, but it is very noticeable in certain Rocky 

 Mountain species. 



It occasionally happens that a form which is a rare 

 variety in one region is the sole representative of the 

 species in a distant region. 



A species of butterfly may feed on a very great 

 variety of different plants, as does our yellow swal- 

 lowtail, or it may feed on only a single kind of plant. 



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