16 
THE HOP APHIS IX THE PACIFIC REGION. 
From these experiments, which were conducted with individual 
insects, it was found that a period of from S to 12 days is required 
for the aphides to pass through the four molts and begin depositing 
vounsr. 
XUMBER OF YOHXG DEPOSITED BY VIVIPAROUS FEMALES. 
Some of the experiments that were carried on to determine the 
number of young that are deposited by individual aphides are 
recorded in Table III. 
Table III. — Number of young deposited by each of 12 individuals of the hop aphis. 
Total. 
X 
Limber 
of young deposited by— 
Date. 
| 
Xo. 1. 
No,2.. 
Xo. .3. 
Xo. 4. Xo. 5. Xo. 6 Xo. 7. Xo. S. Xo. 9. 
Xo. 10. 
Xo. 11. 
Xo. 12. 
4 
5 
7 
4 
/ 
2 
4 
2 

3 
4 

3 
5 
3 
3 
5 
4 
1 
■~> 



13 
14 
4 
3 
2 
3 
3 
4 
4 
2 
8 
3 
3 
3 
4 
4 
9 
3 
5 
2 
3 
I 
1 
3 
3 
4 
5 
3 
5 
4 
3 
3 
2 
2 
5 
15 
10 
17 
IS 
19 , 
20 
1 
1 
3 
4 
2 
5 
4 
3 
6 
5 
2 
6 
3 
3 
3 
2 
21 
1 2 
3 ° 
22 
2 2 
2 3 
9 9 
4 3 
6 
2 
4 

4 
4 
4 
5 
5 
6 
5 
4 
6 
3 
9 
5 
1 
3 
1 
2 
23 
3 
4 
3 
3 
2 
8 
3 
3 
24 
25 
26 
•->- 
5 
5 
8 
4 
4 
6 
4 
6 

7 
1 
2 
1 
4 
2 
1 
3 
2 
4 
2 
4 
4 
3 
1 
4 
1 
1 
1 
28 
29 
30 
Julv 1 
2 
3 
2 3 
8 2 
2 1 3 
1 5 
5 2 
3 6 
2 
4 
1 
S 
3 
2 
2 
4 

1 
1 

1 
3 
1 
5 
4 
6 
4 
3 4 4 3 
6 1 4 ! 3 
6 6 2 6 
4 7 3 4 
12 4 2 
3 3 5 
6 
G 
4 
3 
s::::::::::::::::::::::: :::::::::::: 
9 
1 
1 
10 
12 
13... 
14 
6 2 
5 2 
4 5 
2 o 
1 
1 
2 

2 
2 
1 
15 
2 4 
3 3 
16 
i.x 
4.; 
53 
38 
29 
In order to obtain the foregoing data nearly mature aphides were 
isolated on hop leaves in tin-covered jelly glasses. The leaves were 
changed daily and the aphides which had been deposited were 
removed. The number of young which are deposited by one stem- 
mother were thus found to be from 29 to 92 , with an average of 64 
for the 12 aphides under observation. The length of life of these 
aphides varied from 25 to 38 days, with an average of 30.75 days. 
Thus an aphis living an average life of 30.75 days, depositing an 
