Rau—Longevity in Saturnud Moths. 77 
lated by natural selection for the good of the species, con- 
serving the time which is an advantage to the race and 
curtailing useless existence. 
In short, we must conclude that the longer or shorter 
life of these insects is due to physiological processes, but 
one must also admit that, regulating these physiological 
processes in some way, we have at work natural selection 
carefully seeing that these insects with aborted mouth 
parts have all of their ova at hand ready for ovipositing 
when they emerge from the cocoon, in addition to the 
proper amount of nutriment to give them sufficient length ° 
of life to deposit them, and this even though we know 
not whether the aborted mouth parts are due to the re- 
serve nutriment or the reserve nutriment is there be- 
cause of the aborted mouth parts. 
Hence it would seem that our major problem is one 
not of physiological phenomena alone, nor of heredity 
of longevity alone, but a complex blending of these two 
factors such as can be raveled only by the analysis of 
large quantities of data on varied material. 
