986 
Journal of Agricultural Research vd. xxin, n 0 . h 
Table V.— Relation of temperature and evaporation to rate of development of Aphis 
pomi, iq 20 
Aphid 
series 
No. 
Date of 
birth. 
Date first 
young pro¬ 
duced. 
Develop¬ 
mental 
period. 
Total 
evapora¬ 
tion. 
Average 
daily 
evapora¬ 
tion. 
Mean 
tempera¬ 
ture. 
Duration 
of effective 
tempera¬ 
ture. 
Mean ef¬ 
fective 
tempera¬ 
ture. 
Days . 
Cc . 
Cc . 
° F . 
Days . 
°F. 
I. . 
Mar. 28 
May 3 
36 
453*9 
12 . 6 
45 * I 
23*3 
49-7 
2 . 
May 3 
16 
13 
312.4 
24. 0 
52.6 
10. 4 
57*4 
3 . 
13 
June 1 
19 
412. 6 
21. 7 
5 i *3 
i 4*5 
56.5 
4 . 
16 
3 
18 
406. 0 
22. 6 
51.6 
13*9 
56.5 
5 . 
3 i 
12 
12 
249.1 
20. 8 
56.8 
11. 6 
57*3 
6. 
June 2 
16 
14 
231*5 
16. 5 
55*9 
13*3 
56. 2 
7 . 
9 
21 
12 
216. 8 
18. 1 
57*5 
11. 4 
58.1 
8. 
14 
27 
13 
324.0 
24.9 
57*5 
12. 2 
59*6 
9 . 
i 7 
27 
IO 
274.7 
27*5 
58.2 
9*5 
60.0 
10. 
21 
, 30 
9 
238.1 
26. 5 
59*5 
8.6 
61. 8 
11. 
27 
July 6 
9 
265.3 
29 * 5 
64*5 
8.7 
65.7 
12. 
, 3 ° 
9 
9 
302.7 
33*6 
63.8 
8.7 
63*9 
13 . 
July 7 
18 
11 
218. 8 
19.9 
61.1 
10.9 
61.3 
14 . 
9 
18 
9 
166. 7 
18.5 
61.0 
9.0 
61.1 
15 . 
18 
28 
10 
273.6 
2*4 
62. 5 
9.8 
62. 7 
16. 
28 
Aug. 6 
9 
226.1 
25*1 
64* 5 
8.0 
66.1 
17 . 
Aug. 12 
„ 23 
11 
368.7 
33*5 
63.8 
10. 7 
64*5 
18. 
20 
Sept. 2 
13 
298. 6 
22. 9 
59*3 
12. 0 
60. 2 
*9 . 
20 
11 
22 
406. 6 
18.5 
57*6 
20. 5 
58.6 
20. 
23 
2 
10 
212.9 
21.3 
57*5 
9.0 
59*8 
In general, the records as shown on figure 8 do not coincide exactly 
with the theoretical curve of development. This is no doubt due largely 
to the fact that observations of the aphids were made only once daily, 
which would tend to cause a lagging in the recorded rate of development 
of the insects. Toward the end of the growing season the development 
of the aphids in some of the series was probably retarded to some extent 
by the lack of succulence of the plant tissues, in spite of the fact that the 
most succulent growing tips were selected for rearing; the aphids. The 
extent to which development may be retarded by such a limiting factor 
is shown by series 19, which was reared upon mature foliage. For its 
development this series required a period of effective temperature of 20.5 
days, although accompanied by a mean effective temperature (58.6°) 
high enough to permit development in half the time consumed. This 
effect of the growth of the plant upon the development of Aphis pomi 
was also noted by Baker and Turner, 9 who regard it as a food relationship. 
It is evident that the condition of the foliage of the food plant frequently 
constitutes a limiting factor of considerable importance to the activities 
of Aphis pomi . 
CONCLUSIONS 
Under normal outdoor conditions there is a general correlation between 
atmospheric evaporation and the rate of development of Aphis pomi . 
Atmospheric evaporation, as measured by the standard evaporimeter 
used, does not serve as a satisfactory index to the rate of development 
of Aphis pomi . 
• Baker, A. C., and Turner, W. F. morphology and biology op the green apple aphis. In 
Jour. Agr. Research, v. 5, no. 21, p. 983, pi. 75. 1916. 
