984 
Journal of Agricultural Research voi. xxiii, No.« 
Table III .—Relation of evaporation to rate of development of Aphis pomi , IQIQ —Con. 
Aphid series No. 
Date of birth. 
Date 
first young 
produced. 
Develop¬ 
mental 
period. 
Total 
evapora¬ 
tion. 
Average 
daily evap¬ 
oration. 
Aug. 30 
Sept. 22 
Days. 
24 
Cc. 
392- s 
Cc. 
16. 4 
31 
14 
14 
170.8 
12. 2 
63 . 
Sept. 1 
15 
14 
187.9 
13-4 
64 . 
2 
15 
13 
159.0 
12. 2 
65 . 
3 
18 
15 
170-5 
II. 4 
66. 
5 
J 9 
14 
I83.O 
13. I 
67 . 
6 
19 
13 
182.3 
14. O 
68. . . 
8 
21 
13 
220. 8 
17. O 
69 . 
10 
21 
II 
2II. 6 
19. 2 
70 . 
11 
23 
12 
319.6 
26. 5 
7i . 
13 
28 
IS 
392.6 
96. 2 
72 . 
16 
30 
14 
313-7 
22. 5 
Table IV .—Relation of evaporation to rate of development of Aphis pomi; summary of 
data for igig and ig20 
Length of de¬ 
velopmental 
period. 
Average total 
evaporation 
for period. 
Average 
daily evap¬ 
oration. 
Number of 
records. 
Days. 
Cc. 
Cc. 
36 
453-9 
12. 6 
I 
29 
342.5 
11. 8 
I 
24 
39 2 - 5 
16. 4 
I 
22 
406. 6 
18.5 
I 
19 
412. 6 
21.7 
I 
18 
408. 0 
22. 7 
2 
16 
294.0 
18. 4 
I 
15 
263.3 
17. 7 
6 
14 
236.3 
16. 9 
10 
13 
256.9 
19.7 
10 
12 
263.8 
22.1 
8 
II 
266. 2 
24. 2 
i 5 
IO 
305-2 
30.5 
14 
9 
284. 2 
31.6 
14 
8 
252.4 
3 i -5 
5 
7 
262. 3 
37-5 
2 
TEMPERATURE STUDIES 
The data obtained during 1919 showed that, while there is a general 
correlation between evaporation and the rate of metabolism of Aphis pomi, 
a measure of evaporation alone is not a satisfactory index to aphid devel¬ 
opment. During the summer of 1920 the investigation was continued and 
accurate records of temperature as well as evaporation were maintained. 
The daily maximum, mean, and minimum temperatures for the summer 
of 1920 are given in Table II and are shown graphically in figures 5 and 6. 
It will be noted that there was considerable daily variation in temperature 
ranging from a minimum variation of 7 0 F. on April 1 to the maximum 
variation of 54 0 on August 14. In general, the greatest daily variation 
occurred during periods of high mean temperatures and was correlated 
with a high rate of evaporation. Periods of little daily variation in 
temperature were usually accompanied by low mean temperatures, by 
little evaporation, and frequently by precipitation. 
