578 Journal of Agricultural Research voi. xiii, no. u 



NUMBER OF GENERATIONS ANNUALLY 



From the data on "Length of life cycle," p. 575, the time from ovipo- 

 sition by one generation to oviposition by the next succeeding generation 

 is found to be 28.35 days, the temperature being 79.78° F. In some 

 individuals this time is shortened in the nymphal period alone by at 

 least two days. 



These figures indicate that during the period in which they were col- 

 lected a generation might become mature in less than one month. 

 During the preceding April and May the temperatures averaged respec- 

 tively 53.48° and 61.9°, and during the succeeding October 58.27°. 

 These temperatures were above the average of 49.8° at which incubation 

 proceeded late in October and during November of the same year. 



Observations of 191 3 showed that five generations matured after June i. 

 Hibernating nymphs from 191 3 or overwintered eggs that hatched early 

 in 1 91 4 gave rise to a generation that completed development during the 

 last two weeks of April and oviposited early in May. As the species 

 v/as not reared continuously throughout the year the number of genera- 

 tions annually must be deduced from the data given. 



The writer regards it as conclusive that five generations of the false 

 chinch bug matured at Garden City, Kans., during 191 3 after June i. 

 It is safe to regard this number as the minimum for seasons of the same 

 length. The species hibernates either as an egg or as a young nymph 

 which completes development very early the next spring. At Garden 

 City the overwintering forms matured during April and deposited their 

 eggs early in May. In seasons having temperatures above the average 

 at Garden City the generation hatching from these eggs would become 

 nearly mature by June. 



To summarize : To the minimum of five generations, an overwintering 

 generation and a possible generation in the spring may be added, making 

 seven in all. In seasons in which the average temperature falls below 

 that under which these studies were pursued the number of generations 

 will be less, and with higher average temperatures may become greater. 



