YUCCA MOTH AND YUCCA POLLINATION. 129 
open a dry flower-stalk of any species without finding its 
larva, or examined a green stalk without the evidence of 
oviposition by the female. 
I have often watched the act of oviposition which, though 
simpler, involves much the same motions as in Pronuba. 
The female has more difficulty in making an incision, and 
thissis manifest by the many abortive and tentative attempts 
which she makes in her movements from one part of the 
stem to another. When she has once succeeded in insert- 
ing the ovipositor, and is fairly at work, she becomes as 
sndifferent to examination and interruption as Pronuba, 
under like circumstances, and has often given me time to 
make the accompanying sketch (PI. 39, Fig. 4) in the 
strong glare of the light. The incision always leaves a 
slight discoloration in the stem which becomes still more 
noticeable subsequently and forms a sort of cicatrice. 
(Pl. 38 Fig. 4,a a). The ovipositor—working much as one 
would work the tip of a hand-saw in making an incision — 
cuts achannel at a right angle from the surface and about 
2mm. deep. The oviduct is short — not long and thread- 
like as in Pronuba —and the egg (Pl. 39, Fig. 3, ) is 
found at the base of this channel. The plant-tissues sur- 
rounding the egg seem to be disorganized by the irritation 
somewhat as in the case of Pronuba, and it requires nice 
manipulation to trace the egg which is extremely delicate 
and easily ruptured and in color and appearance closely 
resembles the surrounding tissues. It is compressed, 
elongate and without pedicel. It is, however, plastic and 
variable in form according to position. The apodal larva 
is hatched and begins to burrow about the ninth day after 
the egg is laid and in its curved position and general appear- 
ance, looks much more like some Hymenopterous or some 
Rhynchophorous than a Lepidopterous larva. Itis pellucid 
white in color with black ocelli and brownish mandibles. 
It molts three times, so far as I have have been able to 
trace, acquires full growth in about a month and is then 
more often of a pale emerald-green color. It (Pl. 39, Fig. 
9 
