October, ’20] FENTON AND HARTZELL: POTATO LEAFHOPPER 
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periods of drought, the first extending from early June to early August, 
and the second from the middle of August to the middle of September. 
A maximum high temperature average was reached by the middle of 
June, and lasted until early September, the hottest period coming in 
late July. 
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Experimental Methods 
Data was obtained largely from cage experiments and checked up 
by field observations. The cages were kept in a greenhouse which was 
shaded and well-ventilated and in the fields under as normal condi¬ 
tions as possible. Records on the first or summer generation were 
based on observations made on a plot of early Ohio potatoes at Ames, 
Fig. 13. Life history of Empoasca mail in potato 
Iowa, while the experiments on the second generation were conducted 
on late varieties planted at Ames, and also on late potato fields in 
Mitchell County, Iowa. 
Summary of Seasonal History 
The potato leaf hopper overwintered in the adult stage. These 
adults became active as early as April and were found on various 
weeds until June. They then deserted the weeds and migrated to 
early-planted potatoes as shown by the arrow on the life history chart. 
The females immediately began laying eggs on these vines, and con¬ 
tinued to do so until late July, when most of them died. The first 
nymphs or young appeared on the vines by the middle of June, and 
became especially abundant late in this month and early in July, at 
which time they caused the potato vines to burn badly. By August, 
