MATING HABITS. 23I 



Table 102. Duration of life when the tn-o sexes are separated and not allowed to breed. 



From this table it is evident that the lack of an opportunity for reproduc- 

 tion caused the untimely death of at least half of the beetles experimented 

 upon, but that there was in the population a certain small proportion, espe- 

 cially of the females, that were able to survive for a long period of time. 

 When the beetles are allowed to reproduce normally the death rate is as 

 follows : 



Table 103. Duration of life when beetles are allowed to reproduce normally. 



A comparison of the two tables shows at once that the prevention of nor- 

 mal reproduction produces a decided increase in early mortality, but that in 

 both of the series there are individuals, both male and female, that live to a 

 much greater age than their fellows. This ability of some of the beetles to 

 live for a considerable time has been put to good use in experiment in the 

 preservation of variations which for one reason or another were not able to 

 breed with their own generation, but could be kept alive until reproduction 

 was effected with the generation following. It is quite possible that the same 

 process might occur in nature, where in a restricted locality all the progeny 

 of a given generation were, for some reason, of one sex, and were therefore 

 unable to breed until beetles from another colony should reach the first one in 

 the following generation. The normal length of time between generations in 



