776 The American Naturalist. [September, 
for ovipositing, with the head usually toward the stigma backing down | 
a little, with the body between two of the stamens, her legs straddling 
them. When a favorable point is found, which is generally slightly 
below the middle of the ovary, she rests for a short time, then raising 
the body slightly, thrusts the lance-like ovipositor into the soft tissue of 
the young ovary, penetrating into an ovarian cavity, where it is 
retained for a short time while the egg is being deposited. The ovi- 
positor and oviduct are beautifully modified for this purpose. Ovi- 
position only takes place in newly opened flowers, the first or second 
night after opening, the ovary usually being susceptible to fertilization 
only during these nights. The moth seems instinctively aware of this 
. and never oviposits in an old flower. She evidently in running about 
the flower before oviposition, as explained above, seeks and learns 
whether the flower is in a receptive stage and whether it has been 
already punctured. 
No sooner is oviposition completed than the moth proceeds to the 
act of pollination. She runs to the top of the pistil and bending over 
the stigma, works her head rapidly up and down, forcibly thrusting ` 
the pollen down into the stigmatic tube. The act of oviposition is 
usually followed by the act of pollination. This occurs so regularly 
and promptly that, as Trelease expresses it, “ the moth seems to have 
it on her mind to perform the latter as a sequel to the former.” When 
more than one egg is deposited in the same pistil it is thus pollinated 
more than once, and in some cases where as many as a dozen or more 
eggs are deposited in the same pistil pollination must be very profuse. 
There is a necessity for an abundance of pollen, however, as each of 
the three cells of the ovary contains hundreds of ovules. When the 
load of pollen is exhausted the moth has been observed to replenish 
her supply. 
The larva of Pronuba in its development uses up only from 10-12, 
seeds, so even in those capsules where the most abundant larve develop, 
hundreds of good seeds are nevertheless produced. The few seeds 
destroyed may well be sacrificed to insure the AAEN and develop- 
ment of the others. 
About the time the pod begins to harden the full- -grown larva bores 
its way out, makes its way to the ground, where after boring several 
inches below the surface it forms its silken cocoon. The larva trans- 
forms to the imago state a few days before the flowering of the Yuccas, 
and makes its way to the surface, where the moth escapes. 
The interdependence of Yucca and Pronuba is thus seen to be very 
marked. Ki is a mutual relationshi p closely approaching that of sym- 
