34 BULLETIN C03, U. S. DEPARTMENT OF AGRICULTURE. 
nonresistant X resistant hybrids, it finds its greatest development 
on viniferse and on certain American nonresistant varieties of Vitis 
labrusca, V. aestivalis, and V. monticola. On the wild species of 
Vitis of the eastern and southern parts of North America, consid- 
ered as the original hosts of the grape phylloxera, is found a com- 
plicated life cycle embracing gallicoles (gall lice), radicicoles (root 
lice), winged migrants, sexed forms, winter eggs, and true stem 
mothers. The hibernants are rarely abundant on these wild spe- 
cies of vines, and the winter is passed chiefly in the winter-egg 
stage. On vinifera {Vitis vinifera) this complicated life cycle is 
rarely completed, and a simpler one, comprising only the root forms, 
obtains. Therefore, in the absence of the winter egg, the winter 
period must be tided over by another form, which is supplied in 
the hibernant larva. It appears that, to the phylloxera, Vitis vinifera 
is an acquired food plant, and that the nature and construction of 
the Old World grapevine has changed the habits and life history 
of the grape phylloxera feeding on it. 
On viniferse, although hibernation takes place chiefly on the 
larger roots and on the subterranean portion of the trunk, it occurs 
also on nodosities and on smaller roots. 
Hibernants are located both on lesions and on the normal surface 
of the roots. On the varieties of resistant Amines and certain hybrids 
(vinifera X resistant and resistant X American nonresistant) that 
have been examined, it has been found that hibernation occurs 
chiefly on nodosities and less frequently on the normal root surface. 
Tuberosities rarely are formed on these vines. On American non- 
resistant and vinifera X nonresistant hybrids, hibernation was 
chiefly of the type found on the viniferse. On Golden Champion, 
Agawam, Catawba, Isabella, Lenoir, and Delaware, hibernants oc- 
curred on tuberosities, nodosities, and the normal root surface. On 
Moore's Early they were located on nodosities and on larger roots 
but not on tuberosities. 
Appearance of hibernants. — The hibernants (PL IX, d, e, /, 
p. 64) appear as little oval brown insects flatly appressed to the 
surface of the root, their legs folded underneath the body. The 
antennas are borne at right angles to the major body axis, and hardly 
project beyond the maximum width of the body. The whole insect 
generally shows one color, but sometimes there is a darker median 
longitudinal line, except on the head. In those individuals which 
have molted before going into hibernation, a similar shade of darker 
brown occurs. Occasionally lighter individuals will be noted, but 
none is ever as pale as the growing and feeding radicicole larvae. 
Hibernants located under several layers of bark, as a rule, exhibit a 
paler color than those living more exposed. 
