66 



One of the two hibernating females, born the preceding year, 

 brought forth 109 young between May 30 and July 9. The first- 

 born of these, belonging to the first generation of the year, produced 

 442 young from July 9 to August 22. The first-born of this second 

 generation produced 491 young between August 14 and September 

 28, and the first-born of this third generation brought forth 235 

 young between September 17 and October 25. The earliest descend- 

 ants of this third generation were but partly grown when the winter 

 came on. This fourth generation thus forms, of course, a part of 

 the hibernating group corresponding to that with which the series 

 started. There were thus four generations in a year of this series 

 of the first-born, the number of young for each female of the suc- 

 cessive generations being 109, 442, 491, and 235 respectively — an 

 average of 319 to the generation. The last-born of this hibernating 

 female appeared July 9, but these were lost by the accident mentioned 

 above. 



Turning now to the second female of the hibernating generation, 

 with which a second parallel series of breedings began, we find that 

 this female produced between May 30 and July 15, 186 young of a 

 first generation ; that the first-born of this generation brought forth, 

 between July 12 and August 24, 503 young of the second generation; 

 that the earliest born of these produced, between August 17 and 

 September 29, 528 young of a third generation; and that from the 

 first-born of these, 262 young of the fourth or hibernating generation 

 were produced between September 19 and October 28, We thus have 

 four annual generations of the first-born of this series also, with 186, 

 503, 528, and 262 young in the successive series — an average of 369 

 to the generation. 



The last-horn of the hibernating female with which this second 

 series began appeared July 15, and the last-born of the 498 young 

 produced by this first-generation parent appeared October 1. These 

 were not yet mature when the winter overtook them, and they form 

 a part, of course, of the hibernating group. This gives us but two 

 annual generations of the last-born series — but two "complete" gen- 

 erations—and an average for the year of three generations when both 

 first-born and last-born series are taken into account. 



By reference to the diagram it will be seen that there are three 

 other lines of succession intermediate between these two extremes, 

 and that each of these three lines represents three generations, mak- 

 ing a total of sixteen generations for the five lines or an average, 

 again, of three generations for the whole group. It will also be seen 

 from this diagram that the generations represented by the San Jose 

 scales present and alive in each month were as follows: May, the 

 hibernating generation; June, the hibernating and first generations; 

 July, the hibernating, first, and second ; August, the first, second, 

 and third; September, the first, second and third, and the fourth, 



