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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 31 
these first brood nymphs had largely disappeared, having matured 
into the summer generation of adult hoppers. These began appearing 
on the potato vines early in July and by the middle of this month 
were very numerous. They then migrated to the late potato fields 
which up to this time had been practically free from infestation. On 
them the females laid eggs which hatched into the second brood nymphs 
in late August and early September. These nymphs became espe¬ 
cially abundant during the latter month producing the hopperburn on 
the late potato vines. At the time of frost all immature stages and 
summer brood adults were killed. Second generation adults matured 
from late August on, but did not lay eggs and produce a third brood. 
They remained on the vines until frost, when they flew to various weeds 
and other hardy plants that had not been touched by the cold. Here 
they stayed until these vines in turn were frosted, when they entered 
hibernation. 
Spring Flight 
Adults were found in small numbers feeding on grasses during 
April and early May, but they did not appear in any considerable 
numbers until late in this month, when they were very numerous on 
weeds and grasses. They were especially abundant on the common 
yellow dock, Rum ex crispus L., which they preferred to several other 
kinds of weeds and young apple stock growing near by. Potted potato 
plants were placed among these weeds but were not touched by the 
hoppers. Similar conditions were observed everywhere. In no cases 
were they found on either apple, beans, or potatoes, in spite of the 
fact that they were present in numbers on other plants at this time. 
On the morning of June 6 they suddenly left the weeds and migrated 
in large numbers to the potato plants. This phenomenon was observed 
generally and by several different persons. At this time there had 
been a drop of several degrees in temperature and a light shower. 
Just previous to this, there had been a period of rather high tempera¬ 
ture followed by a rain, during which the mercury had dropped. This 
sudden and complete migration, coming at such a definite time, was 
evidently closely correlated with such climatic factors as temperature 
and humidity, as well as with sexual maturity, for females dissected 
at this time contained the first ripe eggs. At the time of this flight 
late planted potatoes were either not up, or just appearing above the 
soil, and thus were not infested by the hoppers. They remained free 
from these insects until the late July flight of the summer generation 
hoppers, thus proving that there was but one flight of the overwintered 
adults, and that once they had settled on the early potato fields there 
was no further dispersal. 
