LIFE HISTORY. 15 
Table I . — Rate of deposition of young by winged migrants of the hop aphis from prune trtes . 
Date and number deposited. 
Total. 
Became winged. 
May 28. 
May 29. 
May 30. 
May 31. June 1. 
June 3. 
May 28 
1 
2 
1 
2 
4 
2 
1 
1 
7 
Do 
Do 
1 
:::::::::: 
:::::::::: 
i 
5 
3 
.: -.-- 
5 
Do 
May 30 
4 1 1 
1 
8 
1 
Do 
2 
1 
3 
1 


4.3 
1 
The data in Table I were obtained by isolating nymphs, taken 
from the prune trees, upon clean prune leaves in covered jelly glasses. 
When the winged insect appeared 
it was immediately placed upon a 
hop leaf. The deposited young 
were removed daily. 
Fro. 4.— Head of hop aphis, showing frontal tuber- 
cles. Greatly enlarged. (Original.) 
Fig. 5.— Head of melon aphis (Aphis gossypii). 
This aphis is frequently found on hops. Note 
differences in head from that of hop aphis. 
Greatly enlarged. (Original.) 
These young deposited by the 
winged aphides are wingless par- 
thenogenic insects (PL II, fig. 1) . They have the characteristic frontal 
tubercles (see fig. 4, in comparison with fig. 5) and vary in color from 
watery white to green. The very young insects and those that have 
just molted are very light, while the older ones may be quite green. 
RATE OF GROWTH. 
These young aphides grow very rapidly, molt four times, and 
immediately after the fourth molt commence depositing their young, 
as shown in Table II. 
Table II. — Stages in the development of the wingless viviparous female hop aphis. 
No. 
De- 
posited. 
First 
Second 
Third 
Fourth 
molt. 
molt. 
molt. 
molt. 
June 13 
June 15 
June 17 
June 19 
17 
20 
23 
25 
18 
21 
23 
26 
19 
21 
23 
25 
21 
23 
26 
28 
22 
24 
26 
28 
Com- 
menced 
depositing 
young. 
Total 
days. 
1 1 June 11 
2 15 
3 15 
4 16 
5 18 
6 18 
June 20 
27 
27 
27 
29 
29 
