Rau—Longevity in Saturnid Moths. 
affects the longevity of the male one way or the other, 
and hence we see that in the above discussion of the dura- 
tion of life of all mated insects as compared with all un- 
mated insects that the males contribute nothing, or at 
least very little, to the figures showing the unmated in- 
sects to be the longer lived. The responsibility of this 
significant difference must therefore devolve upon the 
females—a very worthy point. So if the males do not 
cause this swinging of the balance, a survey of the tables 
ought to show that the unmated females are longer lived 
than the mated females. And so it does. In absolutely 
every case we find the mean duration of life of the groups 
of unmated females to be the greater by a good margin. 
Here we come to the problem: is the longevity of the 
virgin female the natural length of life, and is it cut 
short by mating, or is the life of the mated female the 
natural one, and without mating is it prolonged, as one 
might think, to give the individual a chance to mate? 
But since we see the unmated Polyphemus living a long 
period, would it be far-fetched to conclude that in the 
mated condition of the Cecropia the life is shortened? 
But whether or not this shortening or lengthening of life 
is of advantage to the species we leave for later discus- 
sion. 
Since the male can be a vagrant and take license as he 
will and not have his number of days reckoned for him, 
and since it seems that the female must pay the price of 
complete living by forfeiture of some days of her life, it 
would be of interest to know precisely how such factors 
react upon organisms higher in the scale of life, say rats, 
poultry, sheep, ete., and from there it would be only a 
step to our own species. 
LONGEVITY AND TEMPERATURE. 
In 1910 when we suspected that low temperature 
tended to prolong the life of the early emerging insects, 
we placed a number of Cecropias in an ice-box, the tem- 
