136 Trans. Acad. Sct. of St. Louts 
ability of the moths on their second or third flights, but well 
balanced tests with large numbers will have to be made before 
we can safely arrive at conclusions. And even if we find that 
the moths liberated for the second or third time are more suc- 
cessful or prompt in returning, the discovery only brings us 
face to face with a more profound problem, viz., are they more 
successful because they actually profit by their experience, or 
because of a finer sensitiveness and superior ability? In other 
words, is their superior ability inherent or acquired? 
The hour of arrival of each of these 214 cynthias was recorded. 
It seems that each of the four species of Saturniids observed 
has a period of flight each night which is constant for that 
species. 
A summary of the cynthia records reveals that for this species 
there are two periods of activity, a primary period from 9 p. m. 
until slightly after midnight, and a secondary one which runs 
from about 3 a. m. until a little after dawn. The peak of their 
activity (see Table 4) is from 10:30 to 11. Of course it is true 
that, early in the term of experimentation, when we had not 
yet fully discovered these habits of flight, we probably inter- 
fered with the natural program of these moths by liberating 
them too late in the evening for them to make their flight 
naturally that night. In a similar event, the cecropias merely 
waited until their regular period the next night, but the eynthias 
were very likely to respond to the call at their second period, 
about dawn. The first is probably their normal period of activ- 
ity, but I am strongly inclined to think that the second is in 
some way influenced by meteorological or dawn conditions. A 
fuller discussion of this complication of primary and secondary 
stimuli will be taken up in the later pages on periodic activity. 
It is interesting to compare the various amounts of time eon: 
sumed by the different moths in making the returns from various 
distances. The records show the exact time for each one of the 
214 males which returned, and the distance traveled. In con- 
sidering the data we must not overlook the fact that where the 
moths did not return before dawn of the same night, since they 
are not active during the day, they had to wait for the darkness 
of the second night; so when the records show that a moth was 
out for 28 hours, it does not mean that this length of time was 
