102 Trans. Acad. Scr. of St. Louis 
Exp. 26. May 24. Wind, east; station, 15 feet west. At 
11:50 p. m. five males were liberated at the edge of the roof 15 
feet from the females, and with the wind blowing directly upon 
them from the cages. Three of the five flew to the cages at 
3:25, 3:40 and 3:55 a. m. This shows clearly that they ean orient 
themselves, even if the distance is short. But more interesting 
is the evidence that, despite the fact that the cages were only 
15 feet away, the moths did not fly to them until dawn, the 
precise moment of their customary flight, almost four hours 
later. This demonstrates, of course, the dominance of a stand- 
ard rhythmic periodicity, but since the moths sometimes react 
to moonlight, one suspects that this periodicity is not regulated 
by the elock, but by a condition of light which acts as a stimnu- 
lant. There was no moon that night. Later experiments show 
that when the moon is bright they sometimes fly to the females 
without waiting for the streaks of dawn to act as a stimulus. 
Exp. 27. May 25. One more female cecropia had emerged, 
while some of the dead ones (functionally speaking), had died, 
so this dawn found three young females and one old one dis- 
played in my windows. These attracted 42 moths from 3:30 to 
4:30 a. m.; this was about half of the number that had come in 
on the preceding day when fewer young females were present. 
This shortage may be explained by either the deficiency of the 
wind, or the probability that yesterday’s response had drained 
the population. Sometimes no wind was perceptible, and again 
there was a faint breeze shifting from one direction to another. 
It may be that returns are better when the wind is stronger, 
for that would clear away the city’s smoke and carry the emana- 
tions more directly. Of the males captured, 41 were native new- 
comers (26 old and 15 young); one bore a mark showing that 
he had come (at this late date) from a two-mile point, as re- 
corded in Exp. 21 on May 22. 
Exp. 28. May 26. I fell asleep that night, and instead of 
going on watch at 3 o’clock as I had planned, it was 4:20 when 
I hastened to the third floor. The rain, which had been falling 
heavily all night, continued. I found a dozen males fluttering 
about the room, and in all probability many had come and gone 
in my tardiness of fifty minutes. However, on account of the 
rain the light conditions were less intense at 4:50 than they 
