105 
days later. The length of the season and other general conditions 
have much influence in determining the number of generations in 
Fig. 3. Cabbage Butterfly, Pontia rapce: a, larva; b. pupa. 
Natural size. 
any year. There are certainly as many as three, on an average, in 
northern Illinois. 
These caterpillars are not only injurious to cabbage, cauliflower, 
and other cruciferous plants, but they sometimes do much damage 
to lettuce. 
Fig. 4. Cabbage Butterfly, Pontia rapcc, male, natural size. 
Fig. 5. Cabbage Butterfly, Pontia rapcr, female, natural size. 
Parasites. — There is hardly a field of cabbage or cauliflower in- 
fested with these green caterpillars in which we can not find masses 
of small white or yellowish cocoons. These cocoons are formed by 
small larvae which live within the bodies of the cabbage-worms, soon 
