128 MISSOURI BOTANICAL GARDEN. 
of Prodoxus and the darker coloring of the under surface 
and tip of abdomen will permit the separation ordinarily, 
and render more careful examination necessary only in 
exceptional individuals of both species, ¢. e., the smaller 
specimens of Pronuba and larger specimens of Prodoxus. 
Closely examined, the female Prodoxus is found to have no 
maxillary tentacles, (there being a mere protuberance in- 
stead at the base of each palpus, Pl. 39, Fig. 2,c.), and in 
fact never makes any effort either to gather pollen or work 
in the stigma. Her ovipositor (Pl. 39, Fig. 3, 6) while 
having a similar construction homologically, is yet a very 
different instrument from that of Pronuba. The male is 
at once distinguished by his longer and darker, differently 
shaped genitalia(Pl. 39, Fig. 3, 7,9). This species does 
not breed in the fruit of the dehiscent Yuccas, but may 
not infrequently be found in that of some of the non- 
dehiscent forms, like alotfolia. The egg is thrust into the 
flower stalk, while this is yet sufficiently tender, and ovi- 
position takes place usually before any of the flowers of Y. 
filamentosa are open. The first specimens are found, as a 
consequence, sometime before the flowering of this species. 
They are most abundant, however, when this Yucca begins 
to flower, and then diminish in number, though a few may 
be found even after the last of the jilamentosa blossoms have 
gone. Thus it is always found associated with Pronuba, but 
in appearance antedates this last and more nearly corres- 
ponds with the blooming of Y. angustifolia, the stems of 
which species it most affects, wherever the two are grown 
together. Prodoxus is, in fact, in large measure dependent 
upon Pronuba, since, as we have already seen, the flower 
stems, especially of Y. filamentosa, die rapidly when 
none of the flowers are fructified, and it is doubtful 
whether Prodoxus could permanently perpetuate itself, 
except as a dependent on the efforts and effects of Pro- 
puba. This species of Prodoxus is common in the South on 
Y. aloifolia, Y.rupicola, Y. gloriosa, and Y. filamentosa, 
and in the west on Y. angustifolia, and I have rarely broken 
