Experiments in Rhythmetic Periodicity 195 
nae removed. If the left antenna is removed, the insect moves 
in a circular direction to the right, and if the right one is re- 
moved, it turns to the left. Now the light came in at the window 
from the right of the insects’ position, and all of them lacking 
the left antenna moved toward the right into the influence of 
the light, while those lacking the right antenna did not drift 
into the path of light and hence did not succeed. Of the moths 
(all females) with both antennae entirely removed, one-third 
came to the light; this is as good a record as any group of able- 
bodied females has ever made for us. This clearly indicates that 
when the female does come to the light she receives the stimulus 
through some organ other than the antennae, although it, 
through mutilation, they are unequal, she may be unable cor- 
rectly to orient herself in making the journey. It is unfortu- 
nate that the lateness of the season prevented our having at 
hand enough males also to thoroughly test this question, but it 
seemed better to keep an adequate supply of them unmodified 
to serve as a check. This they did very well, responding to the 
light to the extent of 96 per cent of their number, thus proving 
that the conditions of the experiment were not at fault. 
The case of the ten females from 2 to 7 days old, with one- 
half of each antenna amputated, is the most perplexing. Since 
females seldom respond to the light to a greater extent than 25 
per cent, I cannot explain why these should have made 100 per 
cent response, except by mere meaningless chance or by some 
intricate arrangement of sense-organs in the basal portion of the 
antenna which we have not yet even suspected. 
The moths with paint-covered eyes made far better returns 
than had been expected; 55 per cent of the males and 7 per 
cent of the females found their way to the light. 
The puzzle remains, what combination of sensory responses 
in relation to environment really brings the sexes together? We 
see the males leaving the females and going to the light, there 
to find their mates, but evidently not following the odor and 
thereby arriving at the light. In this group, since there is so 
much greater response to light when the antennae are mutilated 
than when they are normal, it seems that normally the percep- 
tion of stimuli, either odor or light or both at the same time, 
creates a conflict of feelings in the creatures. If the antennae, 
the organs of perception, are removed, then there follows a 
