98 BULLETIN 903, U. S. DEPAKTMEXT OF AGRICULTURE. 
three daily, at first exceeding that number. These eggs were typical 
radicicole eggs, and produced further radicicole generations. Twelve 
of the eggs laid August 21-24 were transferred to another root of 
the same vine (Thompson's Seedless) and four insects matured 
between September 28 and October 5, after an average egg stage of 
about seven and one-half days and an average growing period of 35 
clays. The progeny of these four became hibernants, several of which 
matured and oviposited the following spring. These experiments 
demonstrate that under California conditions it is possible for larvae 
hatching in galls to mature on the roots and become typical raclici- 
coles. No observations were noted regarding the characteristics of 
the newly hatched gallicoles used in the experiments. After the 
inoculation, July 16. of 50 eggs on the root of the living vine it was 
seen that most of these eggs turned dark brown and failed to hatch. 
The observations on the hatching of this batch of eggs indicate that 
those failing to hatch were the earliest deposited, and it may be that 
the change in conditions and environment affected the embryonic 
development adversely. 
The present nonappearance in California of the gallicole and its 
work on the foliage of grapevines, a condition paralleled in certain 
portions of Europe, vitally affects the entire biology of the insect, 
since it has been ascertained that the phylloxera issuing from the 
winter egg can only exist on the leaf or petiole as a gallicole. The 
Italian investigators Grassi, Topi, Grandori, and Foa found that no 
larva? hatching from winter eggs fastened on the roots and that 
all of this generation of stem mothers (fundatrices) had the galli- 
cole characteristics. This is a very important biological point. It 
is borne out by observations in those parts of Europe where the 
gall form is absent and in which winter eggs are extremely rare. 
It is similarly borne out in the phylloxera regions of California, 
where similar conditions occur. During the winters of 1912-13 and 
1913-14, an extensive series of vines, large and small, of all types, 
many of which had been infested the previous summer with winged 
phylloxera?, and others which, while themselves uninfested, had been 
growing near such infested vines, were examined. With only one ex- 
ception, no trace of winter eggs or dead sexuals was found. This ex- 
ception consisted in the single winter egg noted under the preceding 
heading. 
EFFECTS OF WATER AND HEAT ON PHYLLOXERA. 
Experiments were carried out to determine (1) the resistance of 
hibernant larva? and eggs to water heated to various temperatures, 
(2) the resistance of hibernant larva? to submersion in water at ordi- 
nary temperatures, and (3) the resistance of eggs to the heat of the 
sun. 
