Rau — Longevity in Saturniid Moths. 67 



third case, after a like period of 3 hours, showed a very 

 low per cent, of infertility. 



With so much individuality apparent we cannot yet 

 point out any causal factors of this variability in the 

 fertility of this species. We present the data of the 

 " Fertile Unhatched" column without any more com- 

 ment than to say that here too we find the same variabil- 

 ity as elsewhere; in the ova of some individuals the 

 embryonic mortality is high, and in others comparatively 

 low. Whether or not this lack of viability of the fertile 

 ova is due to some factor in the St. Louis conditions, 

 temperature or humidity, we cannot tell. To be sure 

 this species is typical of the Atlantic states and does 

 not occur at St. Louis, and the environmental conditions 

 here may have affected this material. But the fact that 

 a considerable per cent, of the fertile eggs hatched nor- 

 mally shows that the climate is not intolerable to some 

 of them at least, so the problem remains : What are the 

 special characteristics or weaknesses of certain other in- 

 dividuals which predetermine that they shall not be able 

 successfully to reproduce, or having been produced, to 

 survive ? 



Parallel work was done with 27 fertilized females from 

 Philadelphia, with the results shown in the table below. 

 (See Table 32.) 



In this lot we see an appallingly great degree of in- 

 fertility, and also a much higher per cent, of the fertile 

 eggs which failed to hatch. Of the 4416 eggs deposited 

 by this lot only 1215, or 27.5%, gave forth caterpillars. 

 Even the New York lot, which we considered very weak, 

 gave 41% fertility. Almost one-half of these eggs laid 

 were infertile, and about half of the fertile eggs failed 

 to bring their development to completion. Thus we see 

 this Philadelphia population in a sad plight in regard to 

 their perpetuation. Elimination in the early stages of 

 life is common in all branches of the animal kingdom, 

 but this, an elimination of nearly three-fourths of the 



