GRAPE INSECTS 



457 



ment and becomes mature after the third molt, which occurs 

 in about fifteen days. The forms producing the galls are all 

 wingless females, and each individual of the earher generation 

 may lay from 500 to 600 eggs during the three weeks of her life 

 as an adult. Towards tlu^ end of the season the later broods 

 are not so prolific, 100-200 (^ggs being the maximum. The (»ggs 

 hatch in about eight days, and the young escai)e from the gall 



Fig. 390. — Phylloxera galls on wild grape leaf. 



by the opening on the upper surface of the leaf and migrate 

 to the tender leaves at the end of the branches, where new galls 

 are formed. From five to seven generations of the gall- 

 inhabiting form occurs annually. Nearly all the young of the 

 earlier generations migrate to the leaves, but after the third 

 generation an increasing number migrate to the roots, where 

 they join their underground sisters in their insidious attack 

 on the vine. 



