THE GRAPE LEAFHOPPER IN THE LAKE ERIE VALLEY. 
11 
was present in greater numbers than in the vineyards east of that 
city. This condition also existed in the vineyards surrounding San- 
dusky, Ohio. In vineyards on Kelleys Island, North Bass, South 
Bass, and Middle Bass Islands both T. comes and T. tricincta were 
very abundant and there were also a number of other species and 
varieties in abundance which were not common in vineyards on the 
mainland, the most common being T. vulnerata Fitch. It should be 
stated that in the vineyards east of Cleveland, Ohio, the vines are 
nearly all of the Concord variety, whereas west of that city there is 
a considerable percentage of Catawba and of Early Ohio, while 
around Sandusky, Ohio, and upon the islands the percentage of the 
Concord variety is small, Catawba being the variety most commonly 
Fig. 7. — Three nymphs of Typhlocyba tricincta on underside of grape leaf: a, Cast skin of nymph. Enlarged. 
(Original.) 
grown, as also Delaware, Ives Seedling, Elvira, and a number of 
other varieties used in wine making. In the vineyards on the main- 
land around Sandusky T. tricincta was the species present in destruc- 
tive numbers. T. comes was also present, but only in small numbers. 
Observations in the vineyards of Michigan during the seasons of 1911 
and 1912 showed that T. tricincta is the predominant species in vine- 
yards surrounding Lawton and Paw Paw and in the vicinity of Ben- 
ton Harbor and St. Joseph. In the vineyards of Michigan T. comes 
is present in even smaller numbers than in the vineyards about San- 
dusky, Ohio. 
Although the development of these two species seems to be almost 
identical, adults of T. tricincta brought from the vicinity of Dover, 
