48 



THE MONTHLY BULLETIN. 



dueing the galls are very small and orange-colored. White eggs and 

 the yonng are also to be found within the galls, which are seldom 

 found in California. The root lice are about one twenty-fifth of an 

 inch long and greenish-yellow in summer and a little darker in winter. 



Life History. — During the months of July and August some of the 

 eggs laid by the females of the root forms hatch into individuals which 

 acquire wings. These seek the foliage of the vines and lay large eggs 

 which produce true females and small eggs which produce males. 

 These mate and each female lays a single winter egg upon the bark of 

 the two-year old wood. In the spring this egg hatches into a root 

 form (or gall-making form) which gives rise to the root forms in other 

 stages. These lay eggs which give rise to the many summer genera- 

 tions of devastating root insects. In California the latter hibernate in 

 the soil and may continue for at least four years without reverting to 

 the sexual forms. 



Distribution.— While this pest has been supposed to be limited to 

 the central portions of the State, its appearance in the north seems to 

 indicate that it occurs to some degree in most grape-growing sections 

 north of the Tehachapi. 



Fig.' 38. — The grape phyUoxera (Phylloxera 

 vastairix Planch.). A, Infested grape root; B, galls 

 on leaf ; C, the root louse. 



Food Plants. — This insect feeds upon practically all varieties of 

 grape vines, but is most damaging to the European varieties. Many 

 cultivated varieties and hybrids as well as wild species are slightly 

 attacked, but not so as to greatly impair their growth. These latter 

 are known as resistant vines and are important factors in the selection 

 of roots for vines set out in Phvlloxera-infested districts. While the 



