10 
BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE. 
Table III. — Life cycle of the third generation of Chromaphis juglandicola, San Jose, 
Cal, 1911. 
No. of 
indi- 
vidual. 
1. 
2. 
3. 
4. 
5. 
6. 
7. 
8. 
9. 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
32 
33 
34 
35 
36 
37 
38 
39 
40 
41 
42 
43 
44 
45 
46 
47 
48 
49 
Date of- 
Depo- 
sition. 
May 19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
Acquir- 
ing 
wings. 
June 4 
4 
4 
4 
5 
5 
5 
Life 
cycle. 
Days. 
16 
16 
16 
16 
17 
17 
17 
17 
17 
17 
17 
17 
17 
17 
17 
17 
17 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
19 
19 
19 
19 
19 
19 
19 
No. of 
indi- 
vidual. 
50 
51 
52 
53 
54 
55 
56 
57 
58 
59 
60 
61 
62 
63 
64 
65 
66 
67 
68 
69 
70 
71 
72 
73 
74 
75 
76 
77 
78 
79 
80 
81 
82 
^3 
84 
85 
86 
87 
88 
89 
90 
91 
92 
93 
94 
9.') 
9n 
97 
Date of— 
Depo- 
sition. 
Mav 19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
19 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
22 
Acquir- 
ing, 
wings. 
June 
Life 
cycle. 
Days. 
19 
19 
19 
19 
19 
19 
19 
20 
20 
20 
20 
20 
20 
20 
20 
21 
21 
19 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
21 
21 
21 
21 
21 
21 
22 
22 
22 
23 
23 
23 
24 
24 
Life cycle : Days. 
Maximum 24 
Minimum 16 
Average 19.1 
Generations IV to VIII inclusive occupy roughly 16 days apiece 
for development, and this period is the average life cycle during the 
summer months. Some aphides will develop in 14 days and others 
in 19 or 20. Table IT gives the life-cycle records of these five genera- 
tions and also that of the ninth. The records in some instances are 
small, but the fact that in the first five of these generations there is 
practically no difference in the duration of the life cycle was cor- 
roborated by a larger series of experiments during the summer months 
with individuals of which the respective generations were unknown. 
