﻿THE GBAPE LEAFTTOPPER TN TTfE LAKE ERIE VALLEY. 25 



EXPERIMENTS TO REAR A THIRD BROOD OF NYMPHS. 



Rearing experiments were also conducted to determine if the adults 

 which transformed from the earliest hatching nymphs of the season 

 would produce a second summer brood of nymphs and also if the 

 adults transforming from these second-brood nymphs would mate 

 and produce a third brood of nymphs. 



On July 2, 100 newly hatched nymphs, the product of overwinter- 

 ing adults, were placed on the foliage of a Delaware grapevine in- 

 closed in an arc-light globe cage. By July 28 a few of these nymphs 

 had transformed to adults. By August 14 all of these first-brood 

 nymphs had transformed to adults. On August 26 several nymphs 

 of the second summer brood in the first two nymphal stages were found 

 upon the foliage of the vine. On August 29 all of the adults of the 

 first brood were removed from this cage in order that there might 

 be no confusion with adults transforming from the second-brood 

 nymphs. ~* On September 12 newly transformed adults of the second 

 brood were found in this cage. On September 27 nearly all the 

 nymphs had transformed to adults. The few remaining nymphs were 

 in the last nymphal stage. By October 7 all nymphs had trans- 

 formed to adults. Frequent observations were made after the ap- 

 pearance of the second brood of adults in this cage, but no mating 

 was observed nor did any new nymphs appear on the foliage of the 

 vine. Hence it would appear that reproduction did not occur among 

 the adults of the second brood during the season of 1912. A similar 

 rearing experiment was made on July 3 by taking 75 of the earliest 

 nymphs to hatch and placing them on a grapevine inclosed in an 

 arc-fight globe cage. By July 16 nearly all of the nymphs had trans- 

 formed to first-brood adults. On August 15 new nymphs of the 

 second brood were present. On August 28 all first-brood adults 

 were removed from the cage. All of the nymphs transformed to 

 second-brood adults. Although frequent examinations were made 

 of this cage for the remainder of the season, there was no evidence 

 of reproduction by these adults of the second brood. 



In another rearing experiment the date of transformation of adults 

 of the second brood was secured. The rearings were made by taking 

 nymphs of the first brood that were among the earliest of the season 

 to hatch. They were nearing the last molt when they were placed 

 on a Concord vine in a Riley cage on July 13. By July 16 nearly all 

 of these nymphs had transformed to adults. On July 26 several 

 pairs were observed mating. On August 17 a few nymphs of the 

 second brood in the first and second stages were observed on the 

 grape foliage. On August 28 all adults of the first brood were re- 

 moved from this cage to avoid confusion with newly transforming 

 adults of the second brood. A record of the dates of transformation 

 of adults of the second brood is given in Table X. . 



