THE YUCCA PLANT 
AND ITS 
INSECT ALLY 
F. D. SYNDER, M. D., F. R.G.S. 
One of the Most Remarkable Instances of the Inter- 
relation Existing Between the Animal and the Vege- 
table World, It Would Almost Seem that a Real 
Partnership Existed When the Moth Is Seen At Work 
A BUNDANT wherever the Yucca grows wild, its inseparable com- 
panion in captivity also is the little silvery-white moth of which 
a portrait is shown at the left, hovering beneath the flower as they 
may be seen after nightfall, when their activities on their own be- 
half lead to the indispensable service which they render the plant. 
This is the only known case of an insect deliberately collecting pollen 
from a flower and placing it upon the stigma, and for this reason it 
is perhaps the most extraordinary of all the fascinating phenomena of 
its character. Other remarkable examples of insect pollination are 
known, one being the little wasp which is necessary to the growing 
of Figs; but none quite parallels the definite, purposeful enterprise of 
this strange little Yucca moth 
HE Yucca or Adam’s Needle is a plant that will grow 
where almost nothing else will, as well as on your best 
ground; but it is not to the plant itself that I wish to 
call attention, but to the mode of fertilization that 
Nature has provided for its self-preservation. We are of 
course all familiar with the bees and butterflies that fly from 
one flower to another, their legs and bodies laden with the 
pollen of the flower from which they have just been sipping 
the nectar which they unconsciously scatter in the next flower 
that they visit. But the fertilization of Yucca filamentosa 
SEEDPODS OF THE 
YUCCA 
From these the matured 
larvae of Pronuba yuccasella 
bore their way outward and 
emerge into the light of day 
as the seeds are ripened and 
the pods begin to harden, 
and promptly take to the 
eaith wherein they dwell 
until a final transformation 
brings them forth at last in 
the mature form, just about 
as the Yucca blooms again 
(at right) 
SEARCHING YUCCA 
BLOSSOMS 
If this is done gently and 
patiently during the day- 
time, the moth will surely 
be, come upon sooner or 
later, resting from her in- 
dustrious activities of the 
precedingnight in the moon- 
while chamber of the great 
flower’s calyx where this 
swings aloft on its four to 
five foot stem (at left) 
is done in a more positive way, and leaves one wondering which 
is the more amazing — the marvels of insect or plant life. 
It was the late Professor C. V. Riley, of Missouri, who made 
the discovery of the pollination of the Yucca by a little white 
moth, which he christened Pronuba yuccasella. It is apparently 
the only known instance where a plant is dependent on a single 
species for its pollination, and it is hardly exaggeration to say 
that the plant’s very existence hangs on the existence of this 
insect. In other words if something should exterminate this 
particular little moth, the Yuccas might also soon become- 
extinct. Certainly they would cease to bear seed until they 
had readjusted themselves, at any rate. 
D URING the daytime themoth — sometimes alone, sometimes 
with her mate — may be found with wings partially folded 
resting within the half closed flower. If you carefully open 
some of the blossoms you will come upon the little lady, dressed 
all in white — for she is of a silvery color lighter even than the 
flower in which she is spending the daylight hours. As the sun 
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