306 General Notes. [March, 
therefore, seems readily explained by the principal stated above. 
Whether the mound shall eventually be formed of gravel de- 
pends upon its abundance in the particular locality — F. E. Todd. 
NOTES ON THE BREEDING HABITS OF THE LIBELLULIDÆ.— The 
following observations, though incomplete, are offered because 
there is no prospect that the writer can pursue the subject farther, 
at least not for some time. 
In the month of July, ’82, while camping near Bear creek, Da- 
kota, on a bright, breezy day, his attention was attracted to num- 
bers of dragon-flies hovering over the surface of the water. Many 
of them were in the usual position when pairing. The male 
holding the female by the back of the head with his claspers. 
From the bottom of a deep clear pool various water-plants 
came to the surface, and as the water was rippled by the breeze, 
their tops were occasionally thrown out of the water. Many 
dragon-flies were noticed hovering about, especially around 
the tops of these plants; the female evidently endeavoring 
to gain a footing upon them. In a short time one was suc- 
cessful and immediately folded her wings backward and com- 
menced crawling down the stem into the water. The male 
meanwhile was forced to let go to prevent his being dragged into 
the water. I could see the females until they were about a foot 
below the surface of the water but of course could not trace them 
to the bottom which must have been at a depth of from three to 
five feet. They seemed the more conspicuous because of the quan- 
tity of air which adhered to their abdomen and wings. After 
losing his companion the male hovered about, resting occasionally 
upon the grass at the border of the pool, and evidently watching 
for the return of the female. 
I was unable to determine, very satisfactorily, the length of time 
which the female remained below the surface, but after the first 
after seizing her towed her to shore, being apparently unable to 
lift her from the water. A male falling accidentally upon the water 
was not similarly rescued. The water was more or less infested 
with fish and it seems:not i 
