Rau — Longevity in Saturniid Moths. 75 



been too often committed of placing generalization be- 

 fore accurate and adequate investigation. It will be 

 quite fitting, however, to take the few conclusive results 

 gleaned from this detailed study and construct from 

 them and around them a scheme which would sys- 

 tematize these factors in their relation to the propaga- 

 tion of this small group. 



The very beginning of the adult life shows the simple 

 adaptation to environment which is common to a large 

 proportion of the members of the animal kingdom ; their 

 emergence is accelerated by high temperature early in 

 the season or retarded by late cold. While this would 

 be of advantage only to those species which are inter- 

 ested in vegetation, it is interesting to find the condition 

 existing in these animals also which can have no con- 

 cern for food, excepting for a food-plant upon which to 

 deposit their eggs. In other words, they come out at 

 warm periods, soon to wear themselves out, while they 

 might live much longer if they came out during the colder 

 days, since, as our experiments have shown, cool weather 

 greatly prolongs a quiet life. 



In practically all of this material we find the males 

 emerging before the females. This may or may not be 

 due to the fact that the females have the ova to produce ; 

 nevertheless, the males are on hand for the function of 

 fertilization when the females appear, and hence this 

 delicate adjustment of life, whatever its rise, is an ad- 

 vantage to the species, while it is of no help that we can 

 now see to the individual. 



The homologous length of life of the sexes harmonizes 

 well with the monogamous habit which a large part, at 

 least, of these insects follow. We must acknowledge that 

 it is well for the species that the females are permitted 

 as long a life as they have, in order that they may com- 

 plete their long task of egg-laying. The males on the 

 other hand have a comparatively long, useless period of 

 life after mating. Since polygamy is known to exist in 

 other species of this family, and in some here dealt with, 



