THE WORMS ON THE CABBAGE LEAVES. 15 



of insect life. It existed first as an egg^ then as a larva^ then 

 as a chrysalis, and finally as an adult insect or butterfly. 

 These various changes are commonly spoken of as the tratisfor- 

 motions or life changes of the insect. 



In appearance the two sexes of the butterflies differ slightly 

 from each other. In the males (Fig. 13) there is but one black 

 spot on each front wing, while in the females (Fig. 14) there 

 are two. 



To study the life-history of this insect it is not necessary to 

 raise it from the e^g. Worms of various sizes may be obtained 

 from cabbage plants and reared in glass-covered boxes. They 

 should be frequently provided with fresh, cabbage leaves. The 

 later stages of the insect's life-history may thus readily be 

 observed. 



