578 
Insects and Flowers 
“The full meaning of this wonderful series of operations will not be 
understood until subsequent developments have been followed. Since the 
process of pollination has been so thoroughly done, most of the numerous 
ovules become fertilized and the seeds 
begin their development. In the mean time 
the moth eggs hatch into larvae, which find 
their food in the developing seeds. But the 
seeds are so numerous that the larvae reach 
their growth, gnaw a hole in the seed-pod 
and escape, while many uninjured seeds 
still remain in the pod. The larva spins 
a thread by which it descends to the 
ground, and, burrowing beneath the sur¬ 
face, it passes the winter in its pupal 
state, emerging as a fully developed moth 
at the time of the flowering of the Yucca 
the following summer. 
“It appears that the mature moth takes 
Fig. 7 6 9 * — Pronuba-moth cubbing no f 00( j unless it secures some of the 
pollen down the stigmatic tube of 
Yucca. (After flash-light photo- nectar of the Yucca blossoms in which it 
graph by Stevens; natural size.) j s wont to pass the day, with its head close 
to the bottom of the flower where the nectar 
is excreted. It does not eat the pollen which it gathers, and it seems certain 
that it is prompted to place the pollen in the stigmatic tube after each act 
of oviposition solely by the instinct to provide for its young; for it is readily 
understood that if the ovules are not fertilized the seeds would not develop 
and the larvae would be without food. 
“The Yucca flower, instead of having elaborate devices to secure cross¬ 
pollination, simply prohibits self-pollination by its tubular stigmas and its 
relatively short and reflexed stamens; and then, the sticky pollen and 
an abundance of ovules being provided, the performance of pollination 
is intrusted to the wise instinct of the Pronuba-moth; and not pollina¬ 
tion simply, but cross-pollination, for it has been noticed that it is the habit 
of the moth after securing the pollen to fly to another flower before it begins 
to lay its eggs.” (This extraordinary interrelation between Yucca and 
Pronuba was discovered and carefully studied by C. V. Riley in 1872, and 
his intensely interesting detailed accounts of his observations are to be found 
in Vol. 3 Trans. St. Louis Acad. Sci., his 5th and 6th reports as state ento¬ 
mologist of Missouri, and in the 3d Ann. Rept. of the Missouri Botanical 
Garden). 
The above various and interesting examples of the interrelations between 
flowers and insects are not exceptional cases; indeed this state of affairs 
