44 Trans. Acad. Sci. of St. Louis. 
Péres Ceecropias. The solid lines indicate the number of 
males emerging on the given day, and the dotted lines 
the females. 
In one or two eases, especially the Polyphemus, the 
rate of emergence was so uniform or so scattered that 
this graphic method tells us less than does the simple 
mean. But in most cases the two lines run generally par- 
allel, with only the space of a day or so between them. 
In fact, the nicety with which so nearly every increase 
or decrease in the frequencies of the males is followed 
by a corresponding change in the females is quite sur- 
prising. The female curve follows the male curve like 
its shadow. For instance in the South St. Louis Cecro- 
pias, fig. 6, one could almost estimate from a glance at 
the curves that the males appear on an average between 
1 and 2 days before the females (the calculated mean is 
really 1.84 days). 
Since the males have this precedence in 7 \e the 8 lots 
of material here considered, we feel that it must be more 
than mere coincidence. The Polyphemus (figs. 2-4) show 
this difference less than do the other species; in one lot, 
the Massachusetts Polyphemus (fig. 3) the females show 
a decided priority, and in the other two lots the priority 
of the males is not so great as in the other species. 
But throughout the series of curves we see unexplained 
vacillations in the emergence of the whole population, 
especially in the cases where the lines for both sexes sud- 
denly drop low or to 0 in the midst of the season (as on 
May 22 in fig. 4, and May 10 in fig. 8), or where the 
whole population goes up or down together. Here an- 
other factor becomes apparent. We add to the list of 
figures a curve (the broken line, fig. 9) showing the mean 
temperature for each day, along with the emergence of 
all insects on that day, all species combined. This ex- 
plains at a glance a great deal of the fluctuation of the 
emergence of the entire population, although we cannot 
see that it exerts a particularly greater influence upon 
one sex than upon the other. In a large number of eases 
