84 BUTTERFLIES 



leisurely life for a fortnight or more, thus extending the 

 laying of the eggs over a considerable period. 



About a week after being deposited the egg hatches into 

 a tiny green caterpillar that begins feeding upon the ten- 

 der surface of the cabbage leaf. It is commonly called 

 the cabbage worm and it is doubtless the most generally 

 destructive insect affecting this crop. It continues to 

 feed for several days before the first moult, after which it 

 becomes decidedly larger and begins to eat again more 

 voraciously than before. It undergoes several successive 

 moults during the next two or three weeks before it be- 

 comes full grown as a caterpillar. Unlike most butterfly 

 larvae it has changed very little in its general appear- 

 ance during its growth. It is always of a pale green color, 

 strikingly like the glaucous green of the cabbage leaf, a 

 fact which doubtless helps to conceal it from the eager 

 eyes of birds and other animals. 



When the caterpillar is thus full fed it is likely to leave 

 its food plant and find shelter elsewhere. Sometimes it 

 will stop on the lower surface of the outer leaves, but more 

 commonly it will find a piece of board, an overhanging 

 stone, a fence-post, or the side of a building, where it will 

 prepare for the change to the chrysalis. It will do this 

 by spinning a silken thread upon the surface in which to 

 entangle its hind legs and a loop of silk near by with which 

 to hold its body. When these preparations are com- 

 pleted the insect will cast its last caterpillar skin, emerg- 

 ing as a grayish or brownish chrysalis, the color usually 

 varying with the color of the surrounding surface. The 

 general shape of the chrysalis is shown in plate opposite 

 page 97. 



A week or more later the chrysalis skin bursts open and 



