LEPIDOPTERA 



265 



Only four species have been found in North America; they all belong 

 to the genus Parnassius. Of the four species, two are Alaskan ; the others 

 occur in the mountains of the Pacific States, in Wyoming, and in the 

 Rocky Mountains. Of each of the two latter there are several named 

 varieties. 



Family Pierid^e 



The Pier ids 



These butterflies are usually of medium size, but some of them are 

 small; they are nearly always white, yellow, or orange, and are usually 

 marked with black. They are the most abundant of all our butterflies, 

 being common everywhere in fields and roads. Some species are so abun- 

 dant as to be serious pests, the larvas feeding on cultivated plants. 



In this family the fore legs are well developed in both sexes, there being 

 no tendency to their reduction in size, as in the three following families. 



The larvas are usually slender green worms clothed with short, fine 

 hairs; the well-known cabbage-worms are typical illustrations (Fig. 461). 

 The chrysalids are supported by the tail and by a girth around the 



Fig. 461. — Pieris rapr, larva and pupa. 



middle. They may be distinguished at a glance by the presence of a 

 single pointed projection in front (Fig. 461). 



Our genera of this family can be separated into three groups, which 

 seem hardly distinct enough to be ranked as subfamilies. These are the 

 whites, the yellows and the orange-tips. 



THE WHITES 



The more common representatives of this group are the well-known 

 cabbage-butterflies. They are white butterflies more or less marked 

 with black. Occasionally the white is tinged with yellow; and sometimes 

 yellow varieties of our white species occur. About a dozen North Amer- 

 ican species of this group are known. 



