480 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 17 
of calcium arsenate dust and the percentage of square infested, after the 
beginning of poisoning. 
Table 5. 
Infestation 
Infestation 
Poison 
Date 
Poisoned No. Plots 
Check 
No. Plots Reduction 
Aug. 2. 
5.5 % 1 
18.8 % 
1 
13.3 % 
Aug- 7. 
14. 1 
19.3 
1 
5.3 
Aug. 15. 
15.57 7 
27.71 
5 
12.14 
Aug. 22. 
9.24 11 
34.48 
7 
25.24 
Aug. 29. 
13.03 13 
47.67 
8 
34.64 
Sept. 6 . 
21.66 8 
80.14 
5 
58.48 
The percentage of increase in bloom production of 
poison plots over 
checks is shown 
in table 6. 
Table 6. 
Plat 
August 
Sept. 
No. 
13 
15 
22 29 
4 8 
1 
49 
291 508 
504 
2 
11 
32 59 
313 
3 
17 
78 460 
643 
4 
13 
45 
5 
61 
125 
6 
33 43 
125 
7 
97 
88 
210 
Yield. —The production of seed cotton on comparable plots is given 
in table 7. 
Table 7. 
Plat 
Yield Lbs. Seed Cotton per Acre. 
Increase Lbs. Seed , 
No. 
Check 
Poisoned 
cotton over check 
1 
338 
541 
203 
3 
581 
726 
145 
4 
724 
1085 
361 
5 
1019 
1406 
387 
6 
1019 
1195 
176 
7 
699 
845 
146 
The average increase in yield was 24.45 percent or 236 pounds of 
seed cotton per acre. 
THE IMPORTANCE OF THE FLAXSEED COUNT IN PREDICT¬ 
ING THE ACTUAL FLY-FREE-DATE 
By C. J. Drake, F. A. Fenton and F. D. Butcher, Ames, Iowa 
Abstract 
The period of emergence of either the fall or spring brood of Hessian flies, Phy- 
tophaga destructor Say, varies from year to year with bioclimatic conditions. On this 
account “fixed” or “approved” dates are unreliable and the seeding date each year 
should be correlated with the season and with the fall brood of flies. In Iowa, the 
