﻿THE GEAPE LEAFHOPPER IN THE LAKE ERIE VALLEY. 17 



From this date on, the adults confine their feeding and other activi- 

 ties to the foliage of the cultivated grapevine. About this time the 

 red marking on the elytra disappears and is replaced hy a light lemon- 

 yellow. After the adults once settle down on the foliage of the vines 

 in the vineyards there is very little evidence of further migration, and 

 they seldom leave the shelter of the vines except when disturbed, in 

 which case they fly but a short distance and return almost imme- 

 diately to the underside of the grape foliage. On bright, warm days 

 they become very active on the slightest disturbance of the vine, 

 whereas on cold wet days it is with the greatest difficulty that they 

 are dislodged from the underside of the leaves. 



For several days after their appearance on the foliage ol the -grape- 

 vines the adults confine their activities to feeding on the underside 

 of the foliage. This they do by inserting their threadlike mouth 

 parts or proboscis into the tissue from the underside of the leaf and 

 sucking out the juices. 



TIME OF MATING. 



It is exceedingly rare to find copulating pairs of adult grape leaf- 

 hoppers before migration to the vineyards takes place. After migra- 

 tion to the vineyards mating is not common until a week or ten days 

 of feeding has elapsed. 



The first copulating pair seen during the spring of 1912 was on 

 May 23 upon the foliage of a quince bush in the laboratory garden at 

 North East, Pa. Occasional copulating pairs were seen in vineyards 

 as early as May 25, 26, and 27, but mating did not appear to be gen- 

 eral until about June 1 . After June 5 mating of overwintering adults 

 was rarely seen in the vineyards, although daily observations were 

 made. 



OVIPOSITION OF OVERWINTERING ADULTS. 



No direct observation has been made of females in the act of ovi- 

 position. A number of experiments were made during the summer 

 of 1912 to secure records of egg deposition and the number of eggs 

 deposited by individual females, but without success. This failure 

 was due to the fact that the leaves of all of the varieties of grapes 

 grown in the Lake Erie Valley possess a heavy pubescence or hairy 

 growth on the underside. This makes it extremely difficult to locate 

 the eggs, since they are inserted within the tissue of the leaf beneath 

 this hairy growth and can only be found after a thorough search. 

 Even then many of them are doubtless overlooked, since it often hap- 

 pens that a large number of nymphs will hatch from grape leaves upon 

 which it has been possible to locate only a small number of eggs after 

 a prolonged and careful search. On June 10 the first eggs seen in 1912 

 were located on leaves of a Delaware grapevine. 

 10037°— Bull. 19—14 3 



