102 
Journal of Agricultural Research 
Vol. XIV, No. 2 
that the life of those in the former series was shorter than that of those 
in the latter, the difference, however, not being very great. And if the 
individuals in the A series during the spring of 1915, the third year of 
the experiment, are compared with the individuals in the C series it will 
be noted that the average length of life is also somewhat less in the A 
series than in the C series. An adequate comparison, however, is difficult 
here, as there were fewer individuals in the former than in the latter series. 
In fact, there were only three first-bom individuals in the A series as 
compared with eight first-bom in the C series. 
NUMBER OF GENERATIONS PER YEAR 
A maximum of 33 generations of first-bom individuals was obtained 
in the A series during the first year and a minimum of 9 generations of 
last-bom individuals, making approximately 21 generations for the year. 
The following year (1914) a maximum of 21 first-bom generations was 
reared and a minimum of 7 generations was reared until September, 
when the last generation gave rise to oviparous females. 
The total number of generations for the whole series, as will be noted 
by referring to Table I, was 71 of the first-bom and 18 of the last-bom 
individuals.® 
Table I .—First and last born generations , date of birth , reproductive period in days , 
daily average and. total number of young , total length of life t and maximum and minimum 
temperature during which each generation of Toxoptera graminum lived. Columbia , 
5 . C., 1913-1915 
SERIES A 
Generations. 
Repro¬ 
ductive 
period. 
Young. 
Length 
Of life. 
Temperature. 
First¬ 
born. 
Last- 
born. 
Dates. 
Daily 
average. 
Total. 
Maxi¬ 
mum. 
Mini¬ 
mum. 
1913. 1913. 
Days. 
- 
Days. 
°F. 
°F. 
I 
Mar. 14 to May 
11.. 
28 
2. 64 
74 
58 
93 
42 
2 
26 to 
11.. 
33 
2-33 
77 
46 
93 
42 
3 
Apr. 7 to 
16.. 
22 
4. OO 
88 
39 
93 
42 
4 
. *. 
21 to 
7 - • 
4 
6. 50 
26 
16 
93 
42 
2 
22 to June 
2.. 
32 
i. 28 
61 
41 
97 
42 
S i 
May 3 to May 
28.. 
15 
2. 46 
37 
25 
93 
51 
6 
10 to June 
2.. 
14 
2. 64 
37 
23 
97 
51 
7 
19 to 
27.. 
24 
2.12 
Si 
39 
98 
47 
8 
27 to 
23-* 
17 
1.36 
30 
27 
98 
47 
3 
June 1 to July 
7 -- 
2$ 
’ 2.08 
52 
• 3 6 
100 
47 
9 
4 to June 
26.. 
6 
3.00 
18 
22 
98 
47 
10 
17 to July 
10.. 
IS 
4 * 13 
62 
23 
100 
6 5 
IX 
23 to 
20.. 
17 
2. 82 
48 
27 
100 
65 
12 
30 to 
28.. 
20 
2*75 
55 
28 
102 
65 
4 
July 2 to Aug. 
3 • • 
22 
1. 72 
38 
32 
102 
6 S 
13 
5 to July 
28.. 
17 
3*64 
62 
23 
102 
65 
14 
10 to Aug. 
1.. 
IS 
4 * 13 
62 
22 
102 
69 
IS 
16 to 
8.. 
14 
3 - 7 i 
52 
23 
102 
67 
16 
22 to 
23* 
IS 
4. 66 
70 
32 
96 
66 
17 
28 to 
27.. 
16 
4*75 
76 
30 
96 
61 
5 
29 to 
27.. 
16 
3.68 
59 
29 
96 
61 
18 
Aug. 2 to 
24.. 
12 
4*25 
Si 
22 
95 
61 
19 
8 to Sept. 
7 -* 
17 
3 * 58 
61 
30 
95 
61 
20 
15 to 
2.. 
13 
3-48 
44 
18 
93 
61 
° This table is really a summary of one the writers have prepared showing the date of first and last young, 
daily production, and maximum and minimum daily temperatures, along with other data given here, but 
owing to its large size it could not be included with this paper. 
