THE YUCCA MOTH AND YUCCA POLLINATION. 
BY C. V. RILEY, PH. D. 
PART I, 
INTRODUCTORY. 
Twenty years have nearly passed since the first an- 
nouncement of the method of pollination of our Yuccas by 
the little white Lepidopteron which I christened Pronuba 
yuccasella. The curious facts connected with its structure 
and life habits and its intimate relation with the Yuccas; 
the ease with which it is confounded with the Bogus Yucca 
Moth, found in the same flowers, but possessing no power 
of pollination ; the confusion which the facts have caused 
in the minds of other observers ; the criticism and discussion 
which have followed the observations ; and the opinions of 
others, often based on erroneous observations and conclu- 
sions — have resulted in a number of articles, scattered 
through a number of publications. My friend, Professor 
Trelease, has repeatedly urged me to put together a con- 
secutive statement of the facts in the case, feeling that 
such a statement would prove useful to botanists and 
entomologists alike. It would seem, indeed, eminently 
appropriate to publish such a recapitulation in the Annual 
Report of the Missouri Botanical Garden, in which, while 
its founder was still living, many of the original observa- 
tions, both by Engelmann and myself, were made. 
The present article will fall, naturally, into two parts, 
the first a more popular recapitulation of the facts in re- 
ference to Pronuba yuccasella and Yucca pollination, in 
which will be repeated, almost verbatim, the earlier accounts 
as given in the third volume of the Transactions of the St. 
Louis Academy of Sciences and in my Fifth and Sixth 
Reports on the insects of Missouri, and elsewhere. In the 
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