122 MISSOURI BOTANICAL GARDEN, 
flaccid leaves of this tree Yucca permit much more easy 
study (with the aid of a ladder) of its flowers than of 
Yucca brevifolia, with its stiff, sharp, serrate leaves, which 
form a veritable chevaux-de-frise. Thesmall pod of Yucca 
rupicola from Texas, with its persistent beak-like style, 
also shows the work of Pronuba and is probably pollinized 
by a distinct species, as is also, doubtless, Yucca treculeana. 
I shall be delighted to receive any insects found in or con- 
nected with the flowers or fruit of any of the different 
species from Mexico and the south-west, or even ripe fruit, 
from any one into whose hands this paper may fall, and 
who has had an opportunity of studying the other species 
of Yucca which have not yet been studied in connection 
with pollination. 
Ihave often been struck with the power which the moth 
has of detecting isolated plants blooming for the first time 
remote from other plants or in localities where she could 
not possibly have been previously developed, a fact which 
indicates that, where abundant, in addition to her ordinary 
more sedentary duties, she takes long reconnoitering flights. 
GENERAL CONSIDERATIONS. 
The facts here set forth can be observed by any one who 
will take the trouble to assiduously investigate them. It 
has been a source of frequent pleasure to me to introduce 
my friends to this little moth and its curious ways, and al- 
most every one of my assistants, or those who have been 
associated with me, have been able to verify the facts 
repeatedly, while some of them have been of material aid 
in carrying on the observations ; for these observations are 
more satisfactorily made by two persons than by one, as it 
is difficult for one person to hold the lantern and at the 
same time closely investigate. I would here express my 
particular indebtedness to Messrs. L. O. Howard, E. A. 
Schwarz, Otto Lugger, Albert Koebele, C. L. Marlatt, and 
Th. Pergande, who have aided in the different experiments, 
particularly the latter, who helped me in the earlier ones 
