34 BULLETIN S03, IT. S. DEPARTMENT OF AGRICULTURE. 



nonresistant X resistant hybrids, it finds its greatest development 

 on vinifera? 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 vines 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 

 antennae 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. 



