The Nuptial Flight 129 
doubled. The participants were 9 unmated eynthias, 1 or 114% 
days old, and 12 which had made one or two previous flights. 
None of these ever returned. These five experiments, on the 
evening of June 22, wherein not one of the 91 moths liberated 
in an unfavorable wind returned that night, but a few came 
in later, somewhat justify our surmises in Exp. 24. 
Exp. 30. June 24. Wind, southeast; station, 50 feet west. 
The activity of the moths so far has seemed to indicate that the 
period of flight for this species is about two or three hours 
before midnight. To test this, 36 male cynthias were liberated 
in the back yard at 8:10 p. m., with the wind almost favorable 
for their return. This lot included 6 moths 1% day old, 22 
moths 1 day old, and 8 which had made a previous flight. Of 
these 36, 23 flew up to the cages on the roof; all but two did 
so before midnight, and those two came in only a few minutes 
later. None flew in immediately after having been liberated, 
although we know that they were fully capable of fifty times 
that distance if they would start at once. The first arrived at 
9:16, over an hour after liberation, and the others followed thus: 
9 to 10-8; 10 to 11—9; 11 to 124; 12 to 12:30—2. Since 
none at all came in before this period, although they had ample 
opportunity, and none after (I watched all night for more), 
we are safe in assuming that this is their chosen period of activ- 
ity. By chosen, we mean chosen either by them or by cireum- 
stances, by the combination of stimuli to which they are attuned 
to respond. Since these stimuli or combinations of factors 
usually oecur between these hours, the moths have the habit of 
staging their activities at this period, but if certain of the factors 
or stimuli to which they are attuned to respond are shifted to 
other hours, the moths change their program accordingly. But 
the point that is eternally puzzling to me is: why should the 
hour at dawn be the optimum time for the activity of eecropias, 
and two hours before midnight be likewise the optimum time 
for flight for these near relatives, whose other habits are very 
Similar? : 
The proportion of returns in the various lots of moths is of 
only secondary interest in this experiment, but the data may as 
Well be recorded for use elsewhere. Of the 6 moths, 4 day old, 
2 came in; of the lot of 22 which were 1 day old, 16 returned. 
Of the 8 experienced fliers, 4 had made one flight and 4 had 
