﻿32 BULLETIN 19, U. S. DEPARTMENT OP AGRICULTURE. 



longevity of overwintering adults, number of eggs deposited per 

 female, length of nymphal stages, etc., were covered with a cage 

 early in the season so as to prevent the foliage from becoming 

 infested by other adults. 



Since it was impossible to secure enough Riley cages, or to have 

 cages made that were sufficiently tight to prevent the escape of the 

 adults, recourse was taken to the use of a number of second-hand 

 arc-light globes, which were secured from the local lighting plant. 

 These were about 15 inches high, with a small opening about 4 inches 

 in diameter and a large opening about 8 inches in diameter. The 

 globe was placed over the vine with the lower opening resting on the 

 ground, and the larger opening was covered with a piece of muslin 

 fastened to a stout wire ring. This cover was drawn tightly over the 

 large opening by means of four cords fastened to the wire ring and 

 connected to four pegs driven into the ground and tightened in the 

 same manner as are the cords of a tent. In this way it was possible 

 to draw the muslin perfectly tight all around the edge of the upper 

 opening of the globe. The insects were examined during the cooler 

 part of the day when they were least active. It was found that when 

 the lower opening was set into the ground, the temperature inside of 

 the cage was several degrees higher than that on the outside, owing 

 to a lack of circulation of air inside the cage. This was overcome by 

 taking a strip of fine wire screen about 4 inches wide and forming 

 it into a collar a little larger than the smaller opening of the globe. 

 This collar was then slipped over the young grapevine and pressed 

 firmly into the soil. The globe was then placed over the vine and 

 the small opening fitted into the wire screen collar, thus securing an 

 air current into the bottom of the cage up through the muslin cover 

 or vice versa. The muslin cover was then made large enough to 

 shade the greater part of the globe. These modifications resulted in 

 securing a cage that was light and tight, and that had a temperature 

 about the same as that on the outside. 



The cage that has just been described (see PI. II, fig. 1) is spoken 

 of as an " arc-light globe cage" in connection with the rearing experi- 

 ments mentioned under seasonal history. 



A smaller cage, employed for rearing single nymphs for the purpose 

 of recording the length of the stages of individuals, is fully described 

 on page 26 under another caption dealing with experiments to deter- 

 mine the length of the nymphal stages. 



PARASITES AND PREDACEOUS ENEMIES. 



Apparently the grape leafhopper suffers little from the attack of 

 parasitic enemies. No records of parasites have been found in the 

 literature dealing with this pest. During the investigations on grape 

 insect pests conducted at North East, Pa., from 1907 to 1912, only 



