190 Trans. Acad, Sci. of St. Louts 
(b) if one or the other sex would cross over and reach 
the opposite sex instead of following the light. 
(ec) if these moths would react in the same way to this 
arrangement of stimuli on successive days and 
nights, i. e., as their age and experience advanced. 
An examination at 3:30 a. m. revealed that 14 males, exactly 
one-half, had travelled to the lighted window, diagonally across 
the room from where they had been placed, and one had gone 
along the wall to the adjacent corner and mated with one of the 
females. Not one of the females had moved from where I had 
placed them. At 8 o’clock the next day examination showed all 
of the males (excepting the one in copulo) at the lighted win- 
dow, in the bright sunshine. None of the 28 females had reached 
the light; only four had attempted to do so, but had traveled 
only, 1, 2, 8, and 5 feet. This window faced the street with 
automobile lights also. 
At 9:15 a. m. all the moths were placed in their original posi- 
tions on the wall; 8 returned to the window before noon. It 
seems that they were now breaking down some of their. stiff 
instinets by responding to lights at periods that differed from 
the set rule. ‘These moths were in prime condition, a little more 
than one day old, when 8 out of 28 moved to the light in midday. 
If this reaction to light of this intensity is truly phototropic, 
we should rightfully expect to see all of them respond in the 
Same way, just as they all did to the rays of dawn in the pre- 
vious tests. In Exp. 21, the six males that responded to the 
light during the day were much older than these and, since they 
had failed to do so before, I attributed their reaction to their 
age and experience. The fact that these younger ones behaved 
similarly immediately thereafter leads one to wonder if there 
might be something in the season or the light conditions of these 
late June days which modified their action. 
At noon all of the males were returned to their original places; 
I then had to leave them until 9 p.m. At that time all of the 
males were again on the window and 15 of the 28 females were 
on the sash or near it. 
Exp. 25. June 29,10 p.m. This is a continuation of the last 
experiment, with the same room arrangement, but in addition 
to the 28 males and 28 females, 53 females were also placed at 
the southeast corner of the room. These 109 moths included: 28 
