474 
Journal of Agricultural Research 
Vol. VII, No. ii 
Table IV .—Line of generations of Macrosiphum granarium at Richmond, Ind., in iqo8 
Generation. 
Date of birth. 
Date of first young. 
Age at birth of 
first young. 
Date of last young. 
Productive 
period. 
Life after last 
young. 
. Number of young. 
Average young per 
day of produc¬ 
tive period. 
Largest number of 
young in one day. 
Date of death or 
disappearance. 
Total length of 
life. 
First-bom genera- 
tion series: 
.Days. 
Days. 
Days . 
Days. 
1. 
Mar. 27 
Apr. 
19 
23 
May 26 
37 
12 
38 
1.0+ 
4 
June 9 
74 
2. 
Apr. 19 
May 
9 
20 
May 17 
8 
1 
12 
1. s 
2 
May 18 
29 
3 . 
May 9 
May 
18 
9 
May 27 
9 
4 
16 
1. 7+ 
4 
May 31 
22 
4 . 
May 18 
May 
27 
9 
June 25 
29 
2 
49 
1.6-f- 
4 
June 27 
40 
5 . 
May 27 
June 
7 
11 
June 20 
*3 
2 
IS 
1.1+ 
2 
June 22 
26 
6. 
June 7 
June 
15 
8 
July s 
20 
3 
40 
2 
4 
July 8 
31 
7 . 
June is 
June 
23 
8 
July 4 
11 
1 
29 
2.6+ 
4 
July s 
20 
8. 
June 23 
July 
3 
10 
July 18 
IS 
1 
40 
2.6+ 
5 
July 20 
27 
9 . 
July 3 
July 
11 
8 
July 19 
8 
1 
12 
i- 5 
s 
...do_ 
17 
10. 
July 11 
July 
19 
8 
July 26 
7 
1 
11 
1. 5 + 
2 
July 27 
16 
11. 
July 19 
July 
29 
10 
July 29 
1 
s 
4 
4 
4 
Aug. 3 
15 
12. 
July 29 
Aug. 
6 
8 
Aug. 17 
11 
0 
12 
I. o-l- 
4 
Aug. 17 
19 
13 . 
Aug. 6 
Aug. 
18 
12 
Sept. 9 
22 
0 
35 
I- 5+ 
4 
Sept. 9 
34 
14. 
Aug. 18 
Aug. 
30 
12 
Oct. 13 
44 
13 
26 
• 5 + 
3 
Oct. 26 
69 
15. 
Aug. 30 
Sept. 
11 
12 
Sept. 25 
14 
24 
24 
1. 0+ 
5 
Oet. 19 
So 
16 . 
17 .. 
Sept. 11 
Sept. 29 
Sept. 
29 
18 
Oct. 17 
19 
9 
11 
• 5+ 
2 
Oct. 26 
45 
Last-bom genera- 
tion series: 
2 . 
May 27 
June 
10 
14 
July 1 
21 
3 
10 
.4+ 
3 
July 4 
38 
3 . 
July 1 
July 
13 
12 
July 16 
3 
3 
8 
2.6+ 
4 
July 19 
18 
4 . 
July 16 
Aug. 
3 
18 
Aug. 6 
3 
2 
4 
1. 3 + 
2 
Aug. 8 
23 
5 . 
Aug. 6 
Aug. 
23 
17 
Sept. 5 
13 
4 
13 
I 
2 
Sept. 9 
34 
6 . 
Sept, s 
Sept. 
13 
8 
Oct. 19 
36 
3 
28 
• 7 + 
2 
Oct. 22 
48 
7 ... 
Oct. 19 
The other generation series are not tabulated as there do not seem 
to be sufficiently striking differences to justify it. One generation 
series ran to 18 in the direct line of first born and to 8 in the last 
bom. Other generation series ran below the one tabulated. One female 
in the series not tabulated began producing young at the age of 7 days; 
one female produced 52 young and another lived 79 days. The writer 
has complete records of the number of young produced by 117 females. 
They produced 2,333 young, or an average of 19.9+ young each. The 
average length of time from birth to the production of young for 91 
individuals was 12.6+ days. The average productive period for 99 
individuals was 16.7 days. The productive period for one female (not 
in the tabulated series) was 48 days. The average length of life for 89 
individuals was 34.3 days. 
COLOR VARIATION IN RELATION TO THE SEXES 
All who are familiar with this species of Aphididae will probably recall 
having seen them clustered on heads of wheat just before harvest, and 
noted distinct variation in color. The majority of them at this time are 
strongly tinged with pink. There seems to be no satisfactory explana¬ 
tion for the occurrence of the pink forms at this time. The pink forms 
occur again in October, and this is the signal for the appearance of the 
