THE GRAPE PHYLLOXERA IN CALIFORNIA. 
49 
generation eggs, laid May G to 8, 1912, under an average temperature 
of 63° F., incubated in an average of 10.7 days. 
The results shown in Table VII were obtained during 1911 and 
are in part a complement of those shown in Table VI : 
Table VII. — Incubation records of the eggs of the grape phylloxera, Walnut 
Creek, Calif., 1911. 
Group 
No. 
Environment. 
Average 
tempera- 
ture. 
Month of 
incubation. 
Number 
of eggs. 
Egg stage. 
Average. 
Maxi- 
mum. 
Mini- 
mum. 
1 
E xposed to light 
°F. 
57 
60 
65 
52 
62 
April 
Mav 
43 
177 
352 
16 
323 
15.14 
11.03 
9.07 
15.09 
10.66 
18 
15 
12 
18 
14 
13 
2 
9 
3 
do 
June 
November . . 
May- June... 
8 
4 
...do 
15 
5 
In darkness, laboratory drawer. . . 
9 
The eggs of the first four groups in the preceding table were 
exposed to light on a shelf in the laboratory, and those of group 5 
were incubated in a drawer in the laboratory. Both lots were sub- 
jected to a very abnormal fluctuation of temperature, this fluctuation 
in some cases reaching 20° F. daily. 
In 1912, 1913, and 1915 some additional incubation records were 
obtained, and Table VIII indicates the relations between tempera- 
ture, environment, and incubation to cover the four years, 1911, 1912, 
1913, and 1915. 
Table VIII. — Relation between incubation, temperature, and environment in the 
egg deposition of the grape phylloxera, Walnut Creek, Calif., 1911-1913 and 
1915. 
Lot 
No. 
Year. 
Average 
Number 
daily 
Incuba- 
of eggs. 
tempera- 
ture. 
tion. 
°F. 
Days. 
16 
52 
15.09 
13 
55 
20.50 
26 
56.6 
1 19. 60 
43 
57 
15.14 
17 
59 
15.50 
177 
60 
11.03 
16 
60.5 
15.40 
49 
61 
13.60 
38 
61.3 
15.50 
26 
63 
10.70 
48 
63 
15.50 
28 
63.8 
11.00 
889 
64 
10.80 
10 
64 
13.30 
1,797 
64.5 
10.20 
969 
64.6 
11.70 
286 
65 
10.29 
352 
65 
9.07 
13 
65 
9.40 
20 
67 
9.65 
22 
67.3 
8.80 
22 
68 
9.00 
62 
68 
2 7.00 
21 
68.5 
7.60 
55 
70 
8.90 
61 
70.3 
8.40 
38 
72 
8.70 
Remarks on environment. 
1911 
1915 
1913 
1911 
1915 
1911 
1915 
1911 
1913 
1912 
1913 
1915 
1911 
1911 
1911 
1911 
1911 
1911 
1915 
1913 
1915 
1913 
1915 
1915 
1912 
1913 
1913 
Exposed to light. 
Cellar. 
Do. 
Exposed to light. 
Cellar. 
Exposed to light 
Cellar. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Laboratory drawer— darkness. 
Exposed to light. 
Cellar. 
Do. 
Do. 
Do. 
Do. 
Do. 
Incubator. 
Do. 
Do. 
1 Maximum, 27 days. 
1900°— 21 4 
2 Minimum, 5 days. 
