122 Trans. Acad. Sci. of St. Louis 
eliminates the very difficult factor of proper nutrition of the 
organisms under experimentation. Enough factors remain, how- 
ever, to be considered in these studies,—age of the moths, the 
effect of the wind, weather, fog, moonlight, starlight, lamplight, 
urban odors, ete. Through and under these modifying influ- 
ences, we shall try to discover by what means these moths can 
orient themselves to their mates, and the extent of their abili- 
ties. 
Exp. 1. June 10. Wind, faint breeze from northeast; light 
fog; station, 4% mile southwest. By 11:30 the breeze had be- 
come almost imperceptible and the fog was dense. A dozen fe- 
male cynthias were displayed in wire cages on the roof. Eleven 
males, all 3 days old, were liberated at 9:14 slightly out of the 
path of the wind. Four of these returned at dawn. 
Exp. 2. June 10. Weather same as above; station, 4% mile 
east. Eight young males were liberated at 9:35 p. m. Two of 
these flew to the roof at 3:00 and 3:55 a. m.; the first was found 
resting quietly on a cecropia cage and the other alighted on a 
eynthia cage. 
Exp. 3. June 10. At 3 p. m., when I was painting num- 
bers on the wings of the newly emerged moths, one escaped and 
flew out the window and away, high over the housetops. At 
10:20 that night it came flying back to the cynthia cages as joy- 
ously as if it had not fled the spot a few hours before. 
Exp. 4. June 12. Wind, slight, intermittent breeze from 
west; station, 4% mile east. The 7 males included 5 unmated 
ones % day old and 2 mated ones, 1 day old. They were liber- 
ated in the park at 11:10 p. m. Only one returned, a previ- 
ously mated individual, at 12:20. 
Exp. 5. June 12. Wind, same as Exp. 4; station, 1 mile 
east. For this experiment, we used the 7 moths which had 
already come back from the former test flights and 7 new ones, 
all one day old. All were set free in the park at 11 p.m. Only 
one returned out of these 14; it was 5 days old and had made 
a previous flight, and it made this flight of one mile in three 
hours. At first it was thought that possibly the experienced 
fliers were too old, but since the only one to return was one of 
the old ones, it seems that other factors must have entered into 
the problem. 
