BULLETIN 198. TH E GRAPE LEAF-HOPPER. 201 



and 1908, there was no indication of a third brood. There were two 

 well marked periods of breeding, and none were seen pairing excepting 

 during these periods. For the overwintering hoppers this period was 

 during the last w r eek in April and the first two weeks in May. For 

 the summer brood, or those hatching from eggs laid in May and follow- 

 ing, the breeding period extended over the last week in June and the 

 greater part of July, the maximum pairing occurring about July 10th. 

 The breeding period of this brood is thus seen to be greater than that 

 of the winter brood because of the prolonged hatching period of the 

 preceding generation, while in the case of the overwintering hoppers 

 they all reach maturity at about the same time and pairing takes place 

 within two or three weeks. 



The best evidence of the number of broods is indicated in the well 

 defined periods of breeding, but this fact is further strengthened by 

 the appearance of the nymphs. A couple of weeks after the maximum 

 breeding young nymphs appeared in great abundance, while the 

 appearance of the young gradually diminished as the time from these 

 dates increased. By September 1st very few young nymphs were seen, 

 and all stages of nymphs were gradually disappearing and none at all 

 were seen after October 15th. If there was even a partial third brood 

 it would be expected that young nymphs would be found up to the 

 time the leaves fell from the vine ; but this would not necessarily indi- 

 cate a third brood, for it might be due to the prolonged development of 

 the second brood. The absence of any pairing of individuals of the 

 second brood during the late summer or fall, and the young nymphs 

 ceasing to appear at the normal time after the breeding period of the 

 preceding brood, indicate 'quite clearly that there are two generations 

 of the insect in a year. 



Comparison of Development in Other Localities. At Fresno, one 

 hundred and thirty miles south of Lodi, where the temperature is con- 

 siderably higher than at the latter place, the hoppers go through 

 apparently the same development, although the different stages in 

 the life cycles appear from a week to two weeks earlier than at Lodi. 

 Continuous observation was not made on the hoppers in the vicinity of 

 Fresno, but several trips were made to this section during the season 

 and the life history checked with that of Lodi, except that it was a week 

 or two earlier. In a visit to this territory on October 20th no nymphs 

 were found in any stage, and this would seem to indicate that there 

 are but two broods as at Lodi. 



