60 GENERAL ZOOLOGY 



because its larvae (Fig. 40, c) live on the cabbage plant. The 

 tips of its anterior wings (Fig. 40, a) are grayish. The male 

 has one spot of gray on each of the anterior wings, the 

 female two. There is also a gray spot on the anterior margin 

 of the posterior wings of both sexes. There are several 

 variations of this species ; one form has both sexes entirely 

 white. This butterfly is another insect pest which has come 

 to us from a foreign country, and which has been most 

 prosperous in its adopted home. It first appeared in the 

 region of Quebec about the time of the Civil War. Within 

 twenty-five years it spread from the Atlantic to the Pacific, 

 and from northern Canada to the Gulf of Mexico. In the 

 far north it has two broods and in the south many broods 

 each year. By appearing earlier in the season and having 

 more than one brood a year it has driven out of our gardens 

 the native cabbage butterflies. These are rarely found now 

 except living on the wild relatives of the cabbage. 



The larva of the cabbage butterfly is the familiar green 

 cabbage worm, which eats its way well into the head of 

 cabbage. The native cabbage butterflies (Pi'eris na'pi) 

 which this imported form has so largely replaced were much 

 less destructive, as their larvae feed only on the outer 

 cabbage leaves. 



One of the better-known native species is called the 

 checkered white {Pi'eris protod'ice), so named because of the 

 beautiful, checkered dark and white pattern on the wings 

 of the female. The wings of the male are spotted. 



Economic Importance of Butterflies. In contrast with the 

 moths, which are to be discussed later, the butterflies are 

 practically wanting in destructive . habits. The cabbage 

 butterfly is the only one of really great economic impor- 

 tance. It seems especially fitting that these creatures, which 

 add so much of beauty to man's surroundings, should not 

 be his enemies. 



