160 : PLANT LICE. 
the louse becomes a plump, orange-yellow, full-grown, wingless. 
female, and fills its gall with small yellow eggs, dying soon after. 
The eggs hatch in about eight days into young females again, 
like the parent, and migrate to all parts of the vine to form new 
galls. Six or seven generations of these wingless females fol- 
low one another throughout the summer, frequently completely 
studding the leaves with galls. With the approach of cold 
weather the young pass down the vines to the roots, where they 
remain dormant until spring. The root is then attacked, and a 
series of subterranean generations of wingless females is de- 
veloped. The root form differs but slightly from the inhabitant 
of the léaf galls, and the swellings or excrescences on the roots. 
are analogous to those on the leaves. 
“During late summer and fall of the second year some of 
the root lice give rise to winged females which escape through 
cracks in the soil, on warm, bright days and fly to neighboring 
vines. These winged lice lay their eggs within a day or two 
in groups of two or four in cracks in the bark or beneath loose 
bark on the old wood of the vine and die soon after. The eggs 
are of two sizes, the smaller and fewer in number yielding males 
in nine or ten days, and the larger the females of the only sexed 
generation developed in the whole life round of the insect. In 
this last and sexed stage the mouthparts of both sexes are rudi- 
mentary, and no food at all is taken. The insect is very minute, 
and resembles the newly hatched louse of either the gall or the 
root form. The single egg of the larva-like female after fertil- 
ization rapidly increases in size until it fills the entire body of 
the mother, and is laid within three or four days, bringing us 
back to the winter egg, or starting point. 
“This two-year life-round is not necessary to the existence 
of the species, and the root form may and generally does go on 
in successive broods year after year, as in the case with European 
vines, on the leaves of which galls rarely occur. Under excep- 
tional circumstances all of the different stages may be passed 
through in a single year. The young from leaf-galls may also 
be easily colonized on the roots, and it is probable that the passage 
of the young from the leaves to the roots may take place at 
any time during the summer. The reverse of this process, or 
the migration of the young directly from the roots to the leaves, 
has never been observed. 
