THE BUTTERFLY AND ITS ALLIES 17 



lies of plants especially serve caterpillars as food. Thus of 

 the hundred species of New England butterflies, eight feed 

 upon oaks, eleven upon willows, thirteen upon the Rosacese, 

 and twenty-eight upon leguminous plants. It follows from 

 the restricted food of many caterpillars, that the range of 

 the species must often be determined by that of its food- 

 plant. 



The feeding of the butterfly is mostly done in the larval 

 stage : the pupa can take no food. The imagos of many 

 species touch no food, but in other cases they take small 

 quantities of the nectar of flowers, the sap of plants, and 

 the juice of fruits. 



The imagos fly in the daytime, especially in the sun- 

 shine. Certain species are characteristic of the roadside, 

 others of meadows, gardens, or woods, while still others are 

 found flying everywhere. Owing to its ordinarily short 

 life, the imago is usually found not far from the larval 

 food-plant, upon which it lays its eggs. 



The Broods of Butterflies and their Polymorphism. 

 Butterflies winter over in various stages, some in the egg 

 stage, some as larvse, others as pupse or as imagos. Some 

 kinds pass the winter in either of two stages. In whatever 

 stage they tarry, the life current runs very slow, and dur- 

 ing this season few changes take place. In the spring, 

 development goes on rapidly : the winter generation be- 

 comes mature and a summer generation is started. Fre- 

 quently there is more than one brood produced during the 

 summer, even in the Northern States. Farther south two 

 and even three summer broods are- still commoner. Where 

 two or three broods occur they may be and usually are 

 quite dissimilar. This is very strikingly illustrated in the 

 case of the Zebra Swallow-tail, Iphiclides (JPapilio) ajax, 



