1766 THE BUTTERFLIES OF NEW ENGLAND. 



The butterflies are polygoneutic, at least in the south, probably wintering 

 in the chrysalis. Tlie caterpillars feed upon Gramineae (Erianthus, Zea) 

 and perhaps upon Leguminosae (Wistaria). 



The eggs are large, white, distinctly and finely reticulate with raised 

 lines, and the cells very finely punctuate. The caterpillars are nearly 

 white, sprinkled with darker dots, and according to Abbot faintly striped 

 with green. The chrysalids are greenish white, with a long and slender, 

 straight, tapering frontal prominence. 



Two species are found in eastern North America. 



EXCURSUS LXXVI.—THE COLORING OF BUTTERFLIES AS 

 RELATED TO THEIR DISTRIBUTION. 



WTiite, yellow anil painted, there mustered a score 

 Of the butterflies— with them they brought 'Hei laopo'r. 

 G. C. Sty.^t.— Songs from the Chinese. 



In butterflies as in other animals, species of the widest distribution 

 usually display the greatest variety in their characteristic peculiarities ; no- 

 where is this more true than in their coloring. Latitude, especially, has 

 an influence in these alterations, and altitude produces almost precisely the 

 same effects as latitude. Many species present so different an aspect at the 

 northern and southern extremities of their range as to have been described 

 as distinct species. So we may discover a difference of considerable im- 

 portance in the coloring of butterflies as a whole, in passing from the tropics 

 toward the poles, just as we observe a certain procession of color during the 

 season, as one species is replaced by another. Every one is aware that the 

 most brilliant tints among birds and butterflies are found in the tropics, 

 while the sombre shades are more in sympathy with the gloomier subarctic 

 regions. Prittwitz and Meyer-Diir have studied this question in the 

 European Lepidoptera as a whole, and, with some exceptions, we may 

 accept their generalizations as applicable to the butterflies of our own 

 country. 



The highest life of color in the wings of butterflies consists in sharply 

 defined spots of red, blue, and yellow, and especially of red. These colors 

 predominate in the tropical regions and are rare in alpine and subarctic dis- 

 tricts. As we go north, the colors become less sharply defined, then 

 gradually fade away or become blended with surrounding tints ; the red 

 first disappears, the blue follows, the yellow longest maintaining its hold, 

 although Prittwitz considers the blue the most persistent. As soon as we 

 leave the tropics these brighter colors are seldom seen in combination ; and 

 as we approach the higher temperate regions, we are constantly struck by 

 the impurity of the tints. Take a single example from our common sulphur 

 butterflies of the genus Eurymus ; the more southern species have the 



