64 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 14 



Spite of the fact that practically no males were captured at this earl_v 

 date, the females were fertile and ready to lay eggs. This was brought 

 to our attention by the appearance of first instar nymphs on early 

 planted potatoes June 15, indicating that oviposition was under way 

 by the first week in June. The spring flight occurred June 27, which 

 was three weeks later than last year. Prior to this the females greatly 

 out-nimibered the males but after the flight the sexes were approximately 

 equal. The early appearing females completed egg laying and died 

 the first week in Juh-, while individuals captured at the time of spring 

 flight continued to live until the first week in August. One over-winter- 

 ing female died August 27 after having spent 59 days in captivity. 



VbO- 



Ov 



^ vx-O g. 



/\/ 



y^\A 



\ 



OyVXQ. 



Fig. 1. Curves showing leaf -hopper population correlated with tem- 

 perature: a, Maximum temperature at Ames; ft, Adults; c. Nymphs. 



The number of young produced by the early appearing individuals 

 was approximately one-half the number produced by females captured 

 at the time of the spring flight. The nymphs of the last appearing 

 females reached maturity at a correspondingly late date. These obser- 

 vations and experiments convinced the writer that the overwintering 

 females represented a mixed population. The females appearing out of 

 hibernation early in the spring were probably the remnant of the summer 

 generation of the previous season that had emerged too late to com- 

 plete egg laying and had sunaved the winter to finish it this year. The 

 absence of males in the fore part of the season and the low fecundity 

 could be accounted for in this way. On the other hand it would follow 

 that the adults appearing at the time of the spring flight were individuals 



