150 Annals Entomological Society of America [Vol. XIII, 



trasting with this Quayle in Cahfornia found that this species 

 had two generations and appearing a month and a half earlier, 

 but concluded its development equally early in the fall as is 

 characteristic of the southwest region. The grape leaf hopper 

 had, by practically all superficial workers been credited with a 

 considerable number of generations. Slingerland, by careful and 

 thorough work, reduced this to a possible two. Quayle, under the 

 most favorable possible conditions for a continual production of 

 generations, was unable to find any trace of mating or reproduc- 

 tion in the second brood adults. He did not, however, follow his 

 first generations through and it may possibly be that the second 

 generation was not a complete one even in that region. 



The writer has shown that in the single brooded beet leaf- 

 hopper the nymphal period varies from April and May in Arizona 

 to July and August in Idaho, and that there are all gradations 

 in the intervening regions without changing the single brooded, 

 condition. This species is adapted to feeding on the plants of 

 the beet family and the single generation appears in a region at 

 the time when the food plant is making its most rapid growth. 



The problem of obtaining continuous cage records from gen- 

 eration to generation, with such delicate and active insects as the 

 major portion of the leafhoppers have proved to be, is one of the 

 greatest obstacles to accurate knowledge of this group and no 

 doubt one of the fruitful causes of the mathematical propensity 

 of some of the workers. There are, however, a number of ways of 

 determining what is occurring in the field and in checking up 

 incomplete cage records, even where there is an apparently 

 continuous production of nymphs and adults. The most 

 important single landmark of the season is the mating period. 

 If mating is observed in abundance a new generation will soon 

 follow. This is the time when flights occur, migration takes 

 place, and at this time males often fly to lights in numbers. If 

 on the other hand a great preponderance of females are found 

 it will be the later stages of the egg deposition period. The 

 males are always the first to mature and then there is a short 

 period during which the sexes are equal while the last remnants 

 •of a brood of adults are always females. If males and females are 

 abundant and no mating is taking place, superficial dissection of 

 the female will at once show whether eggs are present. In cases 

 of adult hibernation the fall generation does not mate and no 

 eggs develop that season. 



