Rau — Observations on Samia Cecropia, Linn. 43 



slow decline. The Cecropia motli has about enough vital- 

 ity to fertilize one female ; after that its longer or shorter 

 life is of no consequence to the species. 



Seeing the similarity between the duration of life and 

 the functionless proboscis in Aglia tau and Samia cecro- 

 pia, are we not justified in supposing that Aglia tau is 

 also monagamous, and that the longer duration of life of 

 the male of Aglia tau is one of slow decline and that 

 physically it is unfit to fly actively about after impregna- 

 tion? 



If we suppose Weismann to mean that Aglia tau flies 

 swiftly through the forests before mating, we must con- 

 clude that the species is monagamous. If the species is 

 monagamous, and if the females reject old or middle-aged 

 males, as they do in the cecropia, and considering the 

 physical condition of a moth that has flown through the 

 forests without nourishment for from eight to fourteen 

 days, we can well see how necessary it is for mating to 

 take place while the males are quite young. If it is 

 necessary for the male to mate when very young, in what 

 way can a useless life of the male from 8 to 14 days 

 benefit the race? 



Weismann states that his notes on the life of Aglia tau 

 are not from direct observation, but are estimated from 

 the time when these insects were seen on the wing. It 

 might be possible that further observations on Aglia tau 

 would show that the duration of its life and its habits are 

 somewhat similar to that of Samia cecropia. 



(b) Conclusions. 



Finding the duration of life of the female to be in- 

 sufficient to propagate the race to its fullest extent, and, 

 in contrast to this, an excessive duration of life in the 

 male, which in a species that is monagamous can be noth- 

 ing but useless, we must conclude that the duration of 

 life at this stage of evolution cannot be an adaptation 

 for the good of the species. 



Perhaps the male lives longer because it can accumu- 

 late larger stores of reserve nutriment in the larval 



