Bau — Longevity in Saturniid Moths. 45 



a high frequency corresponds to a high temperature on 

 either the same or the preceding day, and a low fre- 

 quency the corresponding reverse. It is only natural 

 that the parallelism fails after June 10, when at the close 

 of the season only a few stragglers are left to emerge. 

 Two explanations of this phenomenon of priority of 

 male emergence present themselves. The one suggested 

 by Darwin seems at first thought plausible; that among 

 insects as well as among other groups of the animal 

 kingdom the males emerge or arrive at maturity a little 

 earlier than the females in order that they may have 

 time to travel about and seek out mates, and that the 

 first upon the field will win the mates and leave offspring 

 to perpetuate their habits. In this way it is an adapta- 

 tion for the good of the species. But on the other hand, 

 in species like these where the duration of the entire life 

 is but a few days, even these 2 or 3 days of priority of 

 the male may suffice to deprive him entirely of a mate. 

 Hence if this condition exist as a natural law it is at 

 least subject to many drawbacks and defeats by other 

 conflicting factors. The other explanation is that the 

 duration of the pupal life of the male is shorter than 

 that of the female, owing to the fact that the female has 

 the large mass of ova to produce, and that this difference 

 in time required for development becomes apparent at 

 this particular point in the life of the individual. 



Fertility of Saturniid Eggs in Relation to the 

 Mating Period. 



introductory remarks. 



The Saturniid moths, at least the ones with which we 

 have worked, spend much time in mating. The Cecropia 

 moth spends from 10 to 48 hours in copulo, or 21 hours 

 on an average. 12 We have found that a normal mating 

 for all of these species Cynthia, Polyphemus, Cecropia 

 or Californica, consists of a continuous period in copulo 



12 Trans. Acad. Sci., St. Louis, 20: 309, 1911. 



