THE GRAPE PHYLLOXERA IN CALIEORNIA. 
47 
period of egg deposition, the aphids often change their orientation 
by pivoting about the beak. 
Tiirbe of day of oviposition. — Between April 28 and May 25, 1913, 
records were taken in the cellar to obtain data upon the time of day 
of oviposition. The maximum daily temperature occurred about 
6 p. m., 9 and the minimum about 7.30 a. m. Between 9 a. m. and 
5 p. m. (8 hours), 41 eggs were deposited, and between 5 p. m. and 
9 a. m. (16 hours), 52 eggs were deposited in the 27 days. Between 
9 a. m. and 5 p. m., there was an average hourly temperature in 
excess of that occurring between 5 p. m. and 9 a. m. of about 0.02° F. 
It is apparent that the higher temperature of the shorter period 
caused a comparatively greater number of eggs to be deposited, 
since the 52 eggs were laid in exactly double the time in which the 
41 were deposited. 
Egg fertility and mortality. — A large series of experiments took 
place in 1911 to determine the fertility and mortality percentages of 
the eggs of the radicicole phylloxera. These were carried on about 
evenly throughout the year. One series was conducted under cellar 
conditions in petri dishes, and the other took place in the laboratory 
under a higher temperature and was exposed to subdued daylight. 
Table IV gives the results of these experiments : 
Table IV. — Fertility and mortality of the radicicole egg of the grape phylloxera, 
Walnut Creek, Calif., 1911. 
Generation and environment. 
Total 
number of 
eggs 
deposited. 
Number of 
eggs 
hatched. 
Number of 
eggs that 
failed 
to hatch. 
Percentage 
hatched. 
965 
772 
193 
80.00 
1 (Cellar) 
1,000 
490 
911 
422 
89 
68 
91.10 
86.12 
1 (Total) 
1,490 
1,333 
157 
89.52 
2 (Cellar) : 
1,840 
245 
1,716 
236 
124 
9 
93.26 
2 (Exposed to light) 
96.33 
2 (Total) 
2,085 
1,112 
524 
1,952 
133 
93.62 
3 (Cellar) 
987 
486 
125 
38 
88.76 
92.75 
6,176 
5,530 
646 
89.54 
There was no appreciable difference between the fertility of 
those reared in the cellar and of those reared in the higher tempera- 
tures of the laboratory rooms. The results indicate that on the aver- 
age almost 9 eggs out of every 10 laid will hatch. It is probable that 
vineyard conditions produced similar averages as no predators or 
other causes that might bring about a different average have been ob- 
served with the exception of the case of excessive spring moisture 
acting upon the eggs laid by the overwintered adults and in the case 
9 All references to clock time refer to " Standard time." 
