Fig. 262.— P. yuccasella. a, lar¬ 
va; b, female moth with closed 
wings ; c, do. with wings expanded ; 
d, side view of larval segment; 
e, head of larva from below; f, do. 
from above; g, thoracic leg of do. ; 
h , maxilla; i, mandible; j, spin¬ 
neret and labial palpi; k , antenna, 
enlarged. (After Riley, “Insect 
Life,” Vol. IV, p. 360.) 
iTineidse 
pollen with her mouth, which is peculiarly modified to enable 
her to do this, and then applies the pollen to the stigma with in¬ 
finitely better care than it could be 
done by the most skilful horticul¬ 
turist using the most delicate human 
appliances. 
There are several species of the 
genus Pronuba, and they hold a 
positive and well-ascertained re¬ 
lationship to the various species 
of the plants in the economy of 
which they perform so important 
a function. Pronuba yuccasella 
pollenizes in the Eastern States 
the blossoms of the common Yucca 
filamentosa , and on the Western 
plains it performs the act for the 
blossoms of Yucca angustifolia . 
Yucca brevifolia is pollenized by Pronuba synthetica. Yucca 
whipplei is pollenized by Pronuba maculata . No doubt there are 
other species of Yucca which will be ultimately discovered to have 
species of Pronuba which are adapted in their organs to the 
work of pollenation according to their peculiar requirements. 
The larva of Pronuba, after it has attained to full size, drops to 
the ground, having three pairs of thoracic legs, which enable it 
to move about and burrow into the earth. It 
then undergoes transformation into the pupal 
state. The chrysalis, which is depicted in Fig. 
263, has the back armed with peculiar spinous 
processes, which enable it to make its way 
through the loose soil. 
The student who desires to become fully 
acquainted with this interesting chapter in 
insect life must consult the altogether admi¬ 
rable papers written upon the subject by Pro¬ 
fessor Riley, to whom we are indebted for 
almost all that we know in regard to the 
subject. These papers may be found in the 
Publications of the St. Louis Academy of Science, the 
442 
Fig. 263.—P.yuc¬ 
casella. I, male chry¬ 
salis ; m, female chry¬ 
salis. (After Riley, 
“Insect Life,” Vol. 
IV, p. 368.) 
Fifth 
