Experiments in Rhythmetic Periodicity 155 
the mild light of the room was admitted at one end of the box. 
I then created another period of darkness by covering them 
securely for 35 minutes. The cover was lifted again, and during 
a period of 30 minutes not one of the 41 males had moved an 
iota. All of the males were then shifted, as gently as possible, 
to the rear end of the box, and a wire cage containing five young 
females (aged 144 days) was placed at the light end. One 
female proceeded to slowly open and close her wings, and during 
the following ten minutes five males flew to the light end and 
beat against the glass wall. Then a second female began to 
vibrate her wings, and in five minutes three more males came 
out of the dark end and joined in the excitement at the light end 
of the box. With the activity of the males very near to them, 
the excitement of the females ran high. If one suspects that 
cecropia females are entirely devoid of emotions and that they 
mate only by virtue of being passive bundles of odoriferous 
substance, let him watch a group of females placed as these 
were near a group of excited males. First one and then another 
would flutter or vibrate the wings with great rapidity for a 
few minutes; this was followed by a wave of intense excitement 
on the part of the males—one is tempted to call it an agony of 
desperation. The females in their little cage were near the 
light end this time, instead of in the middle as before, and the 
males paid more attention to them than they did in the last 
experiment, and many attempts at mating through the wire 
were made. Strange to say, the females were the more agressive 
in these attempts. At noon the excitement was still high, but 
by 12:15 all had subsided to quietude, with 12 out of the 41 at 
the light end of the box. 
Thus these five females were able to arouse only 12 out of 41 
young males in this ease. This is a much smaller proporiion 
than in the last experiment. The cause of this difference remams 
@ question; there are several possible reasons. First, our day- 
time is their midnight, and we could not expect them to be 
active during their normal period of rest. Second, the males 
may have been too young to be as sensitive and responsive at 
this early age. Again, these had emerged in the laboratory and 
had never had any out-door experience with either the extremes 
and variations of light and darkness, or in responding to the 
