﻿THE GRAPE LEAEHOPPER IN THE LAKE ERIE VALLEY. 



23 



TERMINATION OF OVIPOSITION OF ADULTS OF THE FIRST BROOD. 



First-brood adults placed in cages with grapevines after August 10 

 gave no evidence of further reproduction, for nymphs failed to appear 

 on the foliage. About 50 adults were placed in each of five separate 

 cages on August 12, 15, 20, and 27, and September 9. No nymphs 

 appeared in any of these cages, indicating that the season of egg 

 deposition for them, at least, had closed. 



Since there is a long period over which the nymphs of this first 

 brood transform to adults, an endeavor was made to determine the 

 date at which these later transforming adults would fail to reproduce 

 during the same season. With this end in view, on July 24, 1912, 

 100 nymphs of each of the five nymphal stages were placed in' five 

 separate cages on the foliage of a small Concord grapevine in order 

 to ascertain if the adults transforming from any or from all of the 

 nymphs in these five cages would copulate and produce another 

 brood of nymphs. Frequent examinations were made of all of these 

 cages during the remainder of the season. All of the nymphs in the 

 five cages transformed to adults, but no mating of the adults was 

 observed nor did any nymphs of a new brood appear upon the foliage 

 of the vines in the cages. 



On the other hand, in another cage in which 50 adults were placed 

 on July 22, to determine to what extent and how late in the season 

 they continued to reproduce, nymphs continued to hatch as late as 

 September 15. Below is given the daily hatching record of nymphs 

 from these 50 adults: 



Table VII. — Hatching record of nymphs from 50 adult grape leafhoppers placed in 



confinement July 22, 1912. 





Number 





Number 





Number 





Number 



Date. 



of 

 nymphs 



Date. 



of 

 nymphs 



Date. 



of 



nymphs 



Date. 



of 

 nymphs 





removed. 





removed. 





removed. 





removed. 



1912. 





1912. 





1912. 





1912. 





Aug. 12 



38 



Aug. 22 



143 



Aug. 31 



52 



Sept. 9 



25 



Aug. 13 



132 



Aug. 23 



76 



Sept. 1 



96 



Sept. 10 



13 



Aug. 14 



172 



Aug. 24 



83 



Sept. 2 



108 



Sept. 11 



■ 8 



Aug. 15 



245 



Aug. 25 



50 



Sept. 3 



115 



Sept. 12 



6 



Aug. 16 



173 



Aug. 26 



137 



Sept. 4 



95 



Sept. 13 



4 



Aug. 17 



139 



Aug 27 



108 



Sept. 5 



89 



Sept. 14 



2 



Aug. 19 



272 



Aug. 28 



5 



Sept. 6 



48 



Sept. 15 



6 



Aug. 20 



250 



Aug. 29 



73 



Sept. 7 



49 







Aug. 21 



131 



Aug. 30 



47 



Sept. 8 



24 







LONGEVITY OF OVERWINTERING ADULTS. 



An effort was made to determine the length of lif e of overwintering 

 adults. Owing to the great activity of the adult leafhoppers it was 

 found to be exceedingly difficult to keep a record of each individual- 

 In order to secure some data on this point 100 overwintering adults 

 were placed on a small Concord vine inclosed in an arc-light globe 

 cage on May 31. A black cloth was stretched over the surface of 



