170 Trans. Acad. Sct. of St. Louis 
and early dawn lead the males to activity in the open, natural 
environment, and if the bright light of day induces them to 
rest or perhaps sleep, as it does the owl or bat, one would expect 
the same results in laboratory tests. 
With this question in mind, at 7:30 p. m., a 75-watt electric 
lamp with a reflector behind it, was placed flush against one 
end of the glass box, while the moths were all at the other end. 
Almost immediately one moth flew into the light until it was 
stopped by the glass. This particular male was, it seemed, 
supersensitive to light, for he was without fail, the first one to 
react in every light experiment; he was easily to be distin- 
guished from his companions by black pubescence on his head. 
After ten minutes, two more responded, somewhat languidly, 
and then no more came. These three were marked and replaced 
at the dark end with their companions. After five minutes two 
of these were at the light again, and after two minutes more 
the other marked moth joined them. In a previous experiment, 
eight out of ten responded to dim light; here only three out of 
ten responded to bright light. This shows clearly that the ma- 
jority react to dim light, while only a small proportion are at- 
tuned to the high intensities. One wonders what were the ec- 
eentricities or the special endowments of the one individual 
with the black pubescence that enabled it or drove it always 
to respond first to the lure of the light, both dim and intense, 
while many of his brothers rested. 
One might suspect that fatigue came in about the time this 
test with the bright light was begun, and that for this reason 
few responded. To test this point, I repeated the first part. 
after having kept the moths in the box in darknesss for an hour. 
I then placed the moths in the north end, and uncovered the 
south end of the box next to the small lamp twelve feet away. 
Within ten minutes, eight again out of the ten responded to the 
stimulus by flying to this end. Then I repeated the bright light 
test, placing the 75-watt lamp against the end of the box after 
shifting all of the moths to the other end; it took just twenty- 
five minutes to bring one moth to the light, and no others fol- 
lowed. Once more I tried the dim light. Within two minutes, 
two of the moths reacted, and after ten minutes six were there 
and the other two registered their response by flapping a 
