4 BULLETIN 19, U. S. DEPARTMENT OF AGRICULTURE. 
hibernate, the low-growing foliage of underbrush and shrubs will 
have nearly all of the green coloring matter extracted by this pest 
and present a whitened or sometimes brown appearance before the 
spring migration of the insect takes place. Those adults which winter 
in the vineyards feed upon the green blades and leaves of grasses, 
weeds, and the various plants that are grown as cover crops. When 
the leaves of the cultivated grapevine commence to unfold there is a 
wholesale migration from the foliage of the wild plants, and even 
from the foliage of wild grapevines, to that of the cultivated vines, 
amounting in the course of a week or so. from about May 10 to 25 in the 
region of the Lake Erie Valley, to a complete desertion of the foliage 
of all plants other than those of the wild varieties of grape and possibly 
the Virginia creeper. The percentage of hibernating adults remaining 
on the wild grapevines is very small compared with the number found 
there before the spring migration to the vineyards has taken place. 
It has been observed that in seasons when the infestation through- 
out the vineyard area of the Lake Erie Valley has been light, some 
of the thinner-leaved varieties, such as Delaware and Brighton, are 
apparently more heavily infested and suffer more from the attacks 
of this pest than do the thicker-leaved varieties, such as Concord and 
Niagara. On the other hand, when these insects are very numerous 
throughout a large vineyard area but little if any difference in 
respect to the amount of injury to the different varieties can be 
observed. Usually vines of weak-growing varieties suffer most from 
attack by this pest, yet it has been observed, in run-down Concord 
vineyards in which the foliage was sparse, that reproduction of the 
leafhopper during the summer of 1912 was not so great on such 
vines, even where the overwintering adults were very numerous in 
spring, as in adjacent vineyards where vines of the same variety 
were more vigorous and the foliage was more dense. 
Although many observations have been made to deteirnine if this 
insect reproduces on the foliage of plants other than the wild and the 
cultivated grape, all the evidence secured has been of a negative 
nature. Attempts were made to rear nymphs on the foliage of the rasp- 
berry, which appears to be a favorite food plant of adults when they 
leave hibernating quarters in the spring; A large number of adults 
were confined in Eiley cages containing raspberry plants. Although 
much of the foliage was whitened as a result of their feeding and many 
of the adults lived until about the middle of July, there was no 
appearance of nymphs at any time during the season upon the foliage 
of these plants. All observations during this investigation indicate 
that this insect reproduces only on the foliage of the wild and cul- 
tivated grapes, and that where vines of cultivated varieties are avail- 
able it shows a preference for them and reproduces more freely upon 
them than upon the wild species. 
