THE GRAPE PHYLLOXERA IN CALIFORNIA. 91 
between the larger female and the smaller male egg, but these inter- 
mediate eggs are apparently always of the male sex. Thus there is a 
considerable variation in the dimensions of the male eggs, as, indeed, 
there is in those of the mature male insects. According to Grassi 
(11, p. 134-135) eggs producing females vary in length from 0.384 
to 0.323 mm., and in width from 0.176 to 0.164 mm. ; eggs producing 
males, in length from 0.247 to 0.250 mm., and in width from 0.152 to 
0.134 mm. He also states that eggs of the intermediate dimensions 
are fertile and are of the male sex, and that male and female eggs 
may exceed the limits in one dimension, but never in two. On the 
average the female eggs were slightly larger than the radicicole eggs 
and the male eggs slightly smaller, but intermediate eggs had meas- 
urements identical with those of the radicicoles. 
Measurements of sexual eggs, made in California in 1913, indicated 
a range in length from 0.450 to 0.257 mm., and in width from 0.171 
to 0.117 mm. A single female of these hatched (0.357 by -0.171 mm.). 
In the light of measurements made in 1914 and 1915 it appeared that 
eggs of the sexes were similar in dimensions to those recorded by 
Grassi for Italy, except that the range in sizes was somewhat greater. 
The sexual eggs are bright shining yellow. The eggshell is very 
thin and membranous, quite differently formed from that of the 
radicicole. The egg hatches after about four or five days' incuba- 
tion, the process of hatching consisting in the sloughing off of the 
thin shell, the emerging aphid settling at the place of hatching. 
The eyes and body segmentation become visible, and the undeveloped 
appendages are carried under the body. The insect then undergoes 
four successive molts, and does not move away until it is mature. 
During the first three instars there appears but little change, except 
that the body segmentation becomes more distinct. After the third 
molt the appendages project slightly beyond the sides of the body, 
but otherwise no visible change occurs. All the molted skins are 
contained one within another, adhering to the posterior end of the 
body, and when the last molt has taken place the adult moves away, 
leaving the " nest " of telescoped skins and eggshell behind. It 
sometimes happens that the adult is unable to cast off this pad of 
skins. The mature sexuals are capable of running actively, and, 
according to European investigations, they may live for some weeks, 
thereby facilitating a meeting of the sexes. The sexuals take no 
nourishment. The female is slightly larger and the male slightly 
smaller than the newly hatched radicicole. 
DESCRIPTION. 
THE SEXUAL FEMALE. 
Orange or orange yellow ; antenna? and legs dusky grayish ; antennae longer 
than those of newly hatched radicicole. Body a little longer and wider than 
