THE PIERIDS 



hind wing ; or have one black blotch along the 

 wings outside the middle ; or if it will have the 

 veins of both wings above penciled with gray. 

 All the varieties above mentioned occur ; and to 

 work out the history and different forms of the 

 successive broods and of the several varieties re- 

 quires a mind trained to mathematical precision 

 in methods of thought. To one not thus trained 

 this innocent white butterfly is a source of dire 

 confusion, because its history is so intricate and it 

 masquerades in so man)' guises. The caterpillar 

 feeds upon the outer leaves of cabbage, eating 

 holes in them rather than feeding along the mar- 

 gins. It resembles the caterpillar of P. rapes, 

 except that the dorsal stripe is indistinct and only 

 marked by the absence of the black dots. 



The species is essentially northern, but it spread 

 far south when Pier is rapes was introduced. In 

 some way the European species has greatly re- 

 duced its numbers ; it has literally taken to the 

 woods as a result of this invasion and is seldom 

 found elsewhere. In most of its varieties the 

 gray-veined white is triple-brooded, and winters 

 as a chrysalis. 



77 



