THE FERTILITY OF CECROPIA EGGS IN RELATION 

 TO THE MATING PERIOD. 



PHIL RAU AND NELLIE RAU, 



SAINT Louis, Mo. 



Nature is lavish in her provision and wasteful in her economy. 

 It is often difficult to tell where her reckless generosity ends and 

 where the delicate limitations for the good of the species begin; 

 in how far the individual shapes the race, or how far natural 

 selection or other agencies eliminate the individuals in unnoticed 

 millions in order to make the species the unit. 



The Cecropia moth lays, on an average, about 300 eggs. 

 After a free and natural mating, a considerable portion of these 

 are found to be infertile. May it be that the prolific production 

 thus tends to defeat itself by causing the great elimination? 



We have also found 1 that a large per cent, of the females die 

 still retaining a considerable number of their eggs, which it 

 seems they have not sufficient strength or lease of life to deposit. 

 This waste might also appear the direct result of the strain of 

 producing such a large mass of ova. 



Now we know 2 that the act of mating itself seems to curtail 

 the life of the female by several hours, but even under these 

 conditions of abbreviated time, ovi position is more nearly com- 

 plete than when the individual remains unfertilized. Hence we 

 see that while copulation itself works against the individual in 

 curtailing its life, it works for the race in, in some way, increasing 

 her power of bringing forth her young. In this far we find 

 copulation, besides being a biological necessity, an actual economy 

 in the production of a next generation. 



Now when we consider these phenomena in connection with 

 the fact that on an average 21 hours, or about 9 per cent, of the 

 whole life of the insect, is normally spent in mating, the simple 

 questions at once arise : 



1 Trans. Acad. Sci. St. Louis, Vol. 20, p. 314. 



2 Journ. Exp. Zool., Vol. 12, p. 199. 



245 



