﻿20 BULLETIN 19, U. S. DEPABTMENT OF AGBIOULTUEE. 



Several additional experiments were conducted in the same manner 

 to determine the number of eggs per female. In each case several 

 copulating pairs of leafhoppers were placed in each cage. 



Table III. — Experiment to determine extent of reproduction from four pairs of copu- 

 lating grape leafhoppers placed in a cage with a small grapevine June 19, 1912. 



Nymphs 

 1912. removed. 



July 27 154 



July 30 159 



Aug. 22 8 



Aug. 27 ,.:. 30 



Aug. 29 159 



Total 510 



Average 127. 5 



Table TV. — Experiment to determine extent of reproduction from nine pairs of copu- 

 lating grape leafhoppers placed in a cage with a small grapevine June 18, 1912. 



Nymphs 

 1912. removed. 



July 24 230 



July 31 423 



Aug. 12 172 



Aug. 22 131 



Aug. 29 65 



Sept. 4 14 



Total 1, 035 



Average 115 



Table V. — Experiment to determine extent of reproduction from four pairs of copulating 

 grape leafhoppers placed in a cage with a small grapevine June 19, 1912. 



Nymphs 

 1912. removed. 



July 24 185 



Aug. 9 153 



Aug. 23 58 



Sept. 6 52 



Total 448 



Average 112 



These experiments show that for 20 females the number of nymphs 

 found ranged from 112 to 139 per female. This method of deter- 

 mining the egg-laying capacity of the females did not, of course, 

 take into consideration the number of eggs that failed to hatch, or 

 the number of f atalities which may have occurred among the nymphs 

 after the hatching period, but the fact that the average number of 

 nymphs reared from each of 15 females varied only from 112 to 115 

 would indicate that under favorable conditions a female may deposit 

 over a hundred eggs, while the 139 nymphs obtained in cage 2 would 

 indicate that under the most favorable conditions some females may 

 deposit about 140 eggs. 



