LONGEVITY IN SATURNIID MOTHS AND ITS 
RELATION TO THE FUNCTION 
OF REPRODUCTION.* 
Pui Rav anp Newuie Rav. 
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 fune- 
tions! of the various species, although we cannot say off- 
*Presented by title to The Academy of Science of St. Louis, Novem- 
ber 2, 1914. - 
1 Reproductive function includes brood-care. 
