6 
which goes at once to a young leaf, in the upper surface of which it 
plants its beak. The sucking and irritation soon cause a depression 
to form about the young louse, which grows into a gall projecting on 
the lower side of the leaf. In about fifteen days 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 follow 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 aseries of subterranean generations of wingless females is devel- 
oped. The root form 
CCZ7>3W\W)''’Z differs but slightly 
. J from the inhabitant 
, 3 of the leaf galls, and 
the swellings or ex- 
crescences on the 
= roots are analogous 
all <2 2) to those on the 
y leaves. 
During late sum- 
mer and fall of the 
second year some of 
the root lice give 
rise to winged fe- 
males which escape 

Fia. 3.-—Phylloxera vastatrix. a, migrating stage, winged adult, through cracks in 
b, pupa of same lateral view; c, mouth-parts with thread-like the soil on warm 
sucking setz removed from sheath; d and e, eggs showing char- : 
acteristic sculpturing—all enlarged (original). bright day s 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 mouth- 
parts of both sexes are rudimentary, and no food at all is taken. The 
insect is very minute and resembles the newly hatched louse of either 
the gall or the rootform. The single egg of the larva-like female after 
fertilization 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 usually does go on in successive 
