20 Trans. Acad. Sci. of St. Louis. 
In this table we see only a slight difference in the 
mean duration of life of the mated and unmated males, 
and in this case it is in favor of the unmated individu- 
als; the same is true of the females. When we compare 
the mean for all females with that of all males, we are 
surprised to find a much greater difference, and strangely 
enough, this is in favor of the males. The mean dura- 
tion of life for this entire lot coming from fluffy cocoons 
is 10.72 days, or nearly a day more than the normal 
moths of the same year and place. (See Table 10.) 
When we compare the figures for these two parts of the 
population, we see that the mean length of life is greater 
in the fluffy lot in practically every class. Why should 
it be so unless the insects in the large, fluffy cocoons are 
endowed with greater vigor or a greater supply of re- 
serve energy which carries them just a little further in 
life? May it be that they are thus well supplied with 
reserve nutriment as a direct result of abundant food 
supply of these individuals in the larval stage, and that 
the spinning of the larger cocoons is likewise merely the 
outcome of this accelerated growth? 
Our next lot of material is that known as the South 
St. Louis Ceeropias. Of the 236 insects which emerged 
from these cocoons between May 7 and June 13, 142 fur- 
nished longevity data. (See Table 12.) 
Here we find that the mean duration of life of the 
mated males was greater than that of the unmated ones, 
while just the reverse was true for the females, and here 
too the mean duration of life of all males taken together 
was greater than that of all females. The mean for the 
whole population, 9.32 days, is the lowest of the Cecropia 
lots taken up in this paper, but it is greater than some 
of the 1911 lots. 
The New York Cecropia material consisted of 143 in- 
sects which emerged between May 1 and June 4, 110 of 
which were used for these tabulations. (See Table 13.) 
In this group we find precisely the same relation of 
length of life to sex and mating as in the foregoing lot; 
