August, ’24] 
DRAKE, FENTON AND BUTCHER: HESSIAN FLY 
483 
Page County station, Essex, 1922:—A total of 2,897 eggs were de¬ 
posited on 100 plants during a 24-day emergence period of the fall brood 
from September 16 to October 9, an average of 120.7 eggs per day. 
From the two concentration cages 1,619 flies emerged, and 1,060 were 
caught on the migration screen. The peak of the emergence was 
reached October 1 and the actual fiy-free-date, based on flaxseed 
counts, was announced October 3. Six days later the egg laying period 
for the fall brood was over. The fly-free-date for this county was also 
announced on this same date in 1923. 
Mills county station, Imogene, 1923:—A total of 12,918 eggs were 
laid on 100 plants, during the 32-day emergence period from September 
8 to October 9, an average of 403.6 per day. From the two concentra¬ 
tion cages 2,877 flies issued and 520 were caught on the migration screen. 
The crest of the brood was reached September 29 (Fig. 14). The actual 
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Fig. 12. Graph showing daily egg and fly records at the Monona County District 
Station, Onawa, 1922 
