126 Trans. Acad. Sci. of St. Louis 
In the following group of five experiments, the male cynthias 
were liberated in the evening when the wind was blowing from 
the southeast and it continued in that direction until I returned 
at 4a. m.; there was no moon. Twenty moths, half of which 
had emerged that day and half the day before, were set free at 
9:30; none returned. 
Exp. 21. June 20. Wind, southeast; station, 34 mile north- 
west. Thirty-five male cynthias, 1% day old, were taken 34 mile 
northwest at 9:55. Twelve of these eventually returned, but — 
while all of them came in between the hours of 10:30 and 12:30, 
only one came in the first night (after 114 hours) ; 9 came the 
second night, 1 the third, none the fourth, and one poor wing- 
sore creature straggled in at midnight the fifth night. This 
experiment begins to bring to the fore the factor of rhythmic 
periodicity, which is a fairly well established character in the 
activity of this species. Their habitual] time of flight is between 
10:30 and about midnight; if they do not reach their goal by the 
end of this period, on the first night, they lay over for the same 
hours the next night or even the next. All of these had the 
opportunity to come in at either an earlier or a later hour, but 
not one of the twelve in this experiment did so. 
Exp. 22. June 20. Wind, southeast; station, 4% mile north- 
west. Thirty-eight male eynthias (20 one day old, and 18 two 
days) were set free at 10 p. m. Of these, 22 returned (11 from 
each lot) and, like the last ones, all came between 10:18 and 
midnight. All 22 came back the first night, or in less than 2% 
hours after they had been liberated 14 mile from the cages of 
the females. I do not think the moths in this experiment came 
back more quickly because they were a quarter mile nearer home 
than those in the last test, but probably because they were 
liberated in a current of air more direct from the house. Just 
half of these came in during the first half-hour, 10 to 10:30. 
Exp. 23. June 20. Wind, southwest; station, 1/5 mile east. 
The 38 males, aged 11%4 days, comprised two lots, 20 which had 
never mated and 18 which had mated only a few hours pre- 
viously. The purpose was two-fold: to get additional ecompar- 
ative data on the relation of distance to returns, and to ascertain 
if the mated or the unmated males respond more readily to the 
sex attraction. Of these 38, 20 returned, all but one, the same 
