YUCCA MOTH AND YUCCA POLLINATION. 127 
reason for denying these lowly creatures a degree of con- 
sciousness of what they are about, or even of what will 
result from their labors. They have an object in view, 
and whether we attribute their performances to instinct or 
to reason depends altogether on the meaning we give to 
those words. Define instinct as ‘‘ congenital habit’’ or 
‘‘ inherited association ”’ or, as I prefer to characterize it, as 
the inevitable outcome of organization, and most of the 
doings of the lower animals may justly be called instinctive ; 
but the instinctive and reasoning faculties are both present, 
in most animals, in varying proportion, the last being called 
into play more especially by unusual and exceptional cir- 
cumstances, and the power which guides the female 
Pronuba in her actions, differs only in degree from that 
which directs a bird in the building of its nest, or which 
governs many of the actions of rational men. 
THE BOGUS YUCCA MOTH. 
The natural history of this species, Prodoxus decipiens, 
has been elsewhere recorded ;* but it will be well to show 
here wherein it differs from the true Yucca moth, notwith- 
standing the close general appearance of the perfect insects, 
which resemblance has necessitated the most careful obser- 
vations and has often neutralized those which were care- 
less. The moths (Pl. 39, Fig. 2, a, 6.), in both sexes, 
are on the average considerably smaller than Pronuba, 
and, if anything, more abundant in the earlier opened 
flowers of Yucca filamentosa. The trained observer, how- 
ever, will have no difficulty in distinguishing them, espe- 
cially the females, even without close examination of the 
structure ; for he soon comes to recognize the bull-dog like 
appearance of the head of the female Pronuba, as also the 
difference in the terminal joints of the abdomen, that of 
Prodoxus being thicker and darker. The males are dis- 
tinguished with more difficulty, and yet here the small size 
* Am, Entomologist, III, p. 142; Proc. Am. Ass. Adv. Sc. XXIX, 1880. 
