184 Trans. Acad. Sci. of St. Louis 
male cynthias fly in at dawn just as cecropias do, and others 
even when liberated near the windows where the females are, 
wait until dawn to come in; on moonlight nights they respond 
to some extent to the light of the moon, and they never fly by 
day, although Weed* states that on cloudy days they fly during 
the day. All this, though confusing, indicates that the flight 
of cynthias is regulated by light conditions and that in the eve- 
ning at certain periods and at dawn the light intensities are 
such as to cause response. This, of course, means that cynthia 
finds more periods out of the twenty-four hours when light con- 
ditions are optimum for its activity, whereas cecropia under 
natural outdoor conditions reacts during a very limited period 
of one hour during dawn. Since cecropia with its usual limited 
period for response reacts to light conditions (experimental) at 
any time during the twenty-four hours, what must we expect 
under experimental conditions for cynthia, which has been found 
active at various times of evening, dawn, night and even cloudy 
days? In the face of these difficulties, experiments were under- 
taken to see what their reaction would be to definite light con- 
ditions. Since the glass box was then in use for the cecropia 
experiments, the following tests were made in the third-floor 
room with two east windows. The following year two box ex- 
periments were made, and these are given first. 
Exp. 20. June 23, 1924. At 7p. m., five cynthia moths (3 
females and 2 males) were placed in the glass box and this was 
completely darkened and kept so for thirty hours. At 1 p. m. 
the next day, the cover at one end was lifted, but none flew to 
the light then. When I examined the box at 6:30, none had 
gone to the light, but at 7:30, all had flown to the light end of 
the box. This indicates, of course, that they are not influenced 
to activity by conditions of light or darkness, but that their 
activity oceurs periodically. 
Exp. 21. June 6, 1924. At 7 a. m., twelve eynthias of both 
sexes were placed in the darkened glass box, with the cover 
lifted at the north end. They were given an opportunity durmg 
the entire day to move to the light, but up to 7 o’clock all re- 
mained precisely where they had been placed. Between 7:15 
and 8:05, all but one flew to the light. At this time six more of 
both sexes were added at the light end of the box and the cover 
* Butterflies Worth Knowing, p. 14, 1917. 
