622 ON THE OVIPOSITION OF THE YUCCA MOTH. 
This larva hatches on the fourth or fifth day after the laying of 
the egg, and usually commences feeding between two ovules, 
which, in consequence of its action, swell abnormally. Thus in 
making a longitudinal section of the fruit these swollen ovules 
often indicate the presence of the worm where it would otherwise 
be overlooked while very small. 
While oviposition generally takes place in the manner described, 
the moth head outwards and straddling two stamens, an entirely 
opposite position must sometimes be assumed, since larve and 
punctures are not unfrequently found in the upper part of the 
fruit, especially where a single one is stocked with ten or a dozen 
larvee, as is sometimes the case.* As the fruit enlarges, the mouth 
of the puncture forms a slight, discolored depression, more notice- 
able in some varieties than in others; but the passage-way becomes 
obliterated. 
My observations this summer might be extended much in detail. 
They have convinced me more than ever that Pronuba is the only 
insect by the aid of which our yuccas can be fully fertilized ; for 
I have studied this fertilization diligently night after night, with- 
out seeing any other species go near the stigma. The stigmatic 
opening closes after the first night and I know of no crepuscular 
or nocturnal species which could collect the requisite amount of 
pollen and bring it so to bear on the stigma that each ovule would 
receive the influence of a pollen grain. The species already enum- 
eratedf as frequenting yucca are mostly diurnal and have nothing 
to do in the work; and wherever I have excluded the moth from 
the flowers, by enclosing the latter with netting, no fruit has been 
produced. Iam therefore led to believe that the few rare instances 
of yucca-fertilization, in localities where Pronuba may be presumed 
not to occur, have been brought about by another insect acciden- 
tally, or by the stamens reaching an exceptional length, and the 
anthers being brought into contact with the stigma by the pon 
niving of the closing petals. I have found the stamens of varying 
length in the flowers on the same panicle and in some instances 
almost as long as the pistil. ` 
It is my intention to obtain a large number of cocoons this year 
and it will give me pleasure to distribute them among those who 
*I have counted as many as twenty-one larvæ in a single capsule of what is appar- 
-ently Y. flaccida 
os t Trans. St. Louis Ac. Se., iii, No. 1, p. 59. 
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