WALNUT APHIDES IN CALIFORNIA. 9 
of examples remain immaculate throughout development. The 
"lice" of the second generation develop more quickly than the stem- 
mothers or first generation, owing to greater abundance of food 
supply and to the higher temperature existing at that later period. 
In 1911 second-generation young were deposited in the field on 
early varieties of walnuts a little before April 23, while in the following 
year these were deposited as early as April 6. This is to be expected, 
since in 1912 the trees came out in leaf two weeks earlier than in the 
previous year. Table II shows the life cycle of 41 individuals of the 
second generation at San Jose, Cal., in 1911. 
Table II. — Life cycle of the second generation of Chromaphis juglandicola, San Jose, 
Cal., 1911. 
No. of 
individ- 
ual. 
Date of— 
Life 
cycle. 
No. of 
individ- 
ual. 
Date of— 
Life 
cycle. 
Deposi- 
tion. 
Acquiring 
wings. 
Deposi- 
tion. 
Acquiring 
wings. 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
Apr. 23 
23 
23 
23 
23 
24 
24 
24 
24 
24 
25 
26 
May 1 
1 
1 
1 
2 
2 
2 
2 
May 12 
12 
14 
16 
18 
18 
18 
18 
18 
18 
20 
21 
21 
21 
21 
21 
21 
21 
21 
22 
22 
Days. 
19 
19 
21 
23 
25 
24 
24 
24 
24 
24 
25 
25 
20 
20 
20 
20 
20 
19 
19 
20 
20 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
32 
33 
34 
-35 
36 
37 
38 
39 
40 
41 
May 2 
2 
3 
3 
3 
3 
3 
4 
4 
5 
5 
5 
6 
6 
6 
6 
6 
7 
8 
9 
May 22 
22 
22 
22 
22 
22 
22 
23 
23 
25 
25 
25 
26 
26 
27 
27 
27 
27 
28 
27 
Bays. 
20 
20 
19 
19 
19 
19 
19 
19 
19 
20 
20 
20 
20 
20 
21 
21 
21 
20 
20 
18 
Life cycle: Days. 
Maximum 25 
Minimum 18 
Average 20. 7 
The aphides of the third generation appear on the earliest varieties 
of walnuts about the middle of May, but on the late varieties such 
as the Franquette this brood appears as much as a month later. The 
individuals of this generation are on the average slightly larger than 
those of other generations . In a large series of adult viviparous females 
taken throughout the year of 1911 the largest example was of the third 
generation. Its body was 2.55 mm. in length and 1.06 mm. in width, 
and both of its antennas measured 1.06 mm., or 0.02 mm. in excess 
of the next longest antenna in the series. Table III indicates the life 
cycle of 97 individuals of the third generation. 
40859°— Bull. 100—14 2 
