THE GKAPE LEAFHOPPER IX THE LAKE ERIE VALLEY. 31 
of which there are five. (See PI. I.) The average length of the 
nvmphal period is about 28 days, but with many it varies from 20 
to 35 days. At the last nvmphal molt the adults have fully devel- 
oped wings. A few newly transformed adults may be found in 
vineyards from about July 7 to July 12. 
In normal seasons, however, the majority of the first-brood adults 
appear after the middle of July. Observations of the development 
of the insect indicate that if the nvmphal period is lengthened by low 
temperatures during the month of July, the number of adults of the 
new brood that will mate and deposit eggs for a second brood is 
quite small: whereas, if high temperatures prevail during the early 
part of July, a large number of the nymphs are likely to develop 
rapidly and make their transformation about the middle of July. 
These early maturing adults mate and deposit eggs, and the resulting 
second brood of nymphs is quite large. 
Mating of the first-brood adults appears to be common for only a 
few days. In 1912 few mating pairs were seen except during the 
period from July 23 to July 27. 
Early in August the color markings on the elytra of the adults 
change from light yellow to a pale salmon color, which becomes 
more intense as the season advances. After the appearance of this 
change in coloration of the elytral markings little oviposition occurs. 
By the early part of September most of the nymphs of both the 
first and second broods have transformed to adults, although a small 
number of nymphs may be found on the foliage until quite late in 
the fall. Toward the middle and latter part of September the adults 
commence to migrate from the vineyards and during warm, calm 
afternoons may be seen in swarms drifting through the air in an 
apparently aimless manner. They usually come to rest in adjoining 
woodlands or rough pasture lands. Here they remain more or less 
active during the warmer parts of the days of October and the late 
fall, seeking the shelter of leaves and trash at night and during the 
cooler days, and becoming less active as the cold weather of winter 
approaches. 
REARING CAGES USED. 
Since the adult grape leafhoppers are very agile creatures it was 
impossible to study their habits and life history in detail on the 
large fruiting vines in the open vineyard. Yet in order that the 
adults might oviposit and the eggs develop normally, it was neces- 
sary that the insects studied should be confined on healthy growing 
grape foliage. For this purpose a large number of young grape- 
vines, including several varieties, were planted in the garden of the 
laboratory early in the spring of 1912. The vines were planted in 
rows about 3 feet apart. Those vines used for securing egg records, 
