Experiments in Rhythmetic Periodicity 153 
the females, all flew past the females, ignoring them en route, 
and crowded to the light. Not all the moths behaved alike ; 
only 11 out of the 39 responded thus. This may be explained 
by the fact that this was an off hour for their activity, or by 
the hypothesis that physiologically and psychologically, the 
moths show individual differences. This demonstration shows 
beautifully that it was not the females per se that aroused the 
males, but the odor that emanated from their bodies after they 
had begun to vibrate their wings, and the reaction of the males, 
after having been aroused by the circulating odor, was to fly 
to the light. There were still 28 males that remained unaffected 
at the dark end, the same area from which the 11 active ones had 
come. Why did they not respond? I placed the two females 
in their individual wire cages in the midst of this group, but 
they failed to stir. I prodded the young female with a pencil 
and soon she became intensely active again, vibrating the wings 
rapidly. This aroused to activity some of the 28 males near her, 
and almost simultaneously the eleven at the lighted end, which 
had been quiet for a time, renewed their agitation, rapidly 
vibrating the wings as they moved up and down the glass and 
beat their heads against the barrier. 
Before this one young female had vibrated for one minute, 
three of the 28 males left the crowd and joined the eleven at 
the light end of the box. These were quickly followed by other 
males, and when she quieted down after two and one-half min- 
utes of vibration, there were only 14 left at the dark end of the 
box. Even during the ten minutes following, 6 more males 
responded to the disturbance and flew to the light side, leaving 
only 8 unaffected by her influence. I tried again to prod her 
to activity, but there was no response, perhaps due to fatigue. 
So here were 31 out of 39 males responding to the excitement 
created by this female becoming active and beating the air with 
her wings, while all had been stolidly indifferent so long as she 
had remained quiet and there had been no circulation of air in 
the box, although she was very near to them. The males did 
not all react at the same time; some responded to the stimulus 
Promptly, and others much more slowly. This may indicate 
that some of them were out of the path of the circulation of 
the air at first, but it seems to me more likely that some males 
