28 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 
A/ 
Fig. 4. — Phylloxera vitifoliae: Genealogical graph of the grape phylloxera in the eastern 
part of North America and in the Mediterranean regions. A, Hibernant radicicole ; 
B—G, successive radicicole generations ; H, winged sexuparous migrant ; I, sexes ; 
J, stem-mother gallicole ; K-P, successive gallicole generations, part of the young larvse 
of which proceed below ground (Q) to join the radicicole circle at various stages de- 
pendent upon the gallicole generation of which they w^ere members ; Z, emergence above 
ground of the wandering radicicole larvse. In this figure, in order to avoid undue con- 
fusion, no account has been taken of the development in the galls of winged sexuparous 
migrants. Such development is unusual, but it indicates the possibility of a life cycle 
entirely aerial. 
