146 
JOURNAL OF ECONOMIC ENTOMOLOGY 
]Vol. 11 
noticeably, and by the latter part of the month had become compara¬ 
tively rare. 
After migration, the eggs were deposited on apple. Nymphs of 
the second generation appeared during the middle of July, and during 
early August the adults of this generation occurred in numbers. The 
nymphs of the second generation reached their greatest abundance 
during the last week of July and the first week in August. From this 
time on, the nymphs became less numerous, and by early October, had 
become rare, although at this time the adults were numerous on apple. 
Migration now occurred from the apple to the rose, where the winter 
eggs were deposited. 
Empoasca mali. The observations made at Geneva during this 
study show that this species hibernated largely, if not exclusively, in 
the adult form. During the winter, three dozen one- and two-year-old 
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Fig. 6. Life-cycles of apple leaf-hoppers as observed at Geneva, New York, during 
the seasons of 1915 and 1916. 
apple stock were planted in the greenhouse. Numbers of leaf-hopper 
nymphs soon emerged from eggs deposited in the bark. The appear¬ 
ance of the nymphs was such that they might easily have been mis¬ 
taken for Empoasca mali , but when the adults developed, they proved 
without exception to be Empoasca unicolor. No nymphs of the former 
species appeared. 
In the orchards, nymphs of E. mali appeared in numbers during the 
last ten days in June. This is obviously too early for the appearance 
of nymphs of the second generation, and is much too late for the hatch¬ 
ing of the winter egg, had hibernation taken place in that stage. 
There was considerable variation in the ages of the nymphs of this 
first generation, and the more advanced matured in early July. By 
the middle of July, the great majority of the nymphs were in the later 
instars and the adults were becoming very numerous. Nymphs of the 
second generation began to appear during the latter part of the month, 
