LONGEVITY IN SATUENIID MOTHS AND ITS 



EELATION TO THE FUNCTION 



OF REPRODUCTION.* 



Phil Rau and Nellie Rau. 



Introduction. 



If Nature's aim in the animal world be the improve- 

 ment of the races, she must have a frequently changing 

 medium upon which to operate ; if it be merely their per- 

 petuation, she may be satisfied with a few well favored 

 individuals which live a long time. The first hypothesis 

 concentrates attention upon the welfare of the race, the 

 second on the welfare of the individual. But the pur- 

 poses of Nature seem two-fold, both perpetuation and 

 improvement of the stock. 



It is obvious that the improvement would best be ac- 

 complished by the production of the maximum number 

 of young in connection with a brief duration of life, thus 

 giving a large number of tender individuals for Natural 

 Selection to play upon, and many generations in a brief 

 period of time through which to effect changes. This 

 plan, however, could not hold good for all the members 

 of the earth's animal population, for it would not permit 

 of the development of size, strength and high differen- 

 tiation of organisms — all these factors pertaining to the 

 individual welfare. 



A momentary mental survey of the animal world will 

 tell us that a marked correlation exists between the 

 length of life of individuals and the reproductive func- 

 tions 1 of the various species, although we cannot say off- 



♦Presented by title to The Academy of Science of St. Louis, Novem- 

 ber 2, 1914. 



i Reproductive function includes brood-care. 



(1) 



