INSTINCTIVE BEHAVIOUR IN INSECTS 83 
pellet of pollen from the anthers, proceeds to another flower, 
pierces the pistil with her sharp ovipositor, lays her eggs 
among the ovules, and finally darting to the stigma stuffs the 
pollen pellet into its funnel-shaped extremity (Fig. 14). If 
the flower be not thus fertilized 
the ovules do not develop; and 
if the ovules do not develop the 
grubs which are hatched from the 
moth’s eggs die of starvation. 
There are enough ovules to supply 
food to the grubs, and leave a 
balance to continue the race of 
Yuccas. 
Whether the female moth is 
attracted to the flower by sight 
or smell, we do not know. And _ Fie. 14.—Yucca Flower and 
whether the male finds the female, oe 
in the case of the Yucca moth, through scent, we are not 
in a position to state with certainty. It has, however, been 
shown that in certain moths* some odour emitted by the 
female is the attractive stimulus, affecting sense-organs situated 
on the antenne of the male. To females confined in an opaque 
vessel over the mouth of which gauze was tied, the males came 
in numbers; but when a clear glass vessel was inverted, and 
sand was packed round the mouth, so as to prevent the escape 
of air from the interior, no males came, though the imprisoned 
females were clearly visible. If the antenne of the males were 
either removed or coated with shellac the moths failed to 
notice the females even when close to them. In what way the 
intact male is made aware of the direction from which the 
scent comes, we do not know—possibly by differential stimula- 
tion in the antenne, the moth instinctively turning in the 
direction of greater stimulation. It will be seen, therefore, 
that in the case of the behaviour of the Yucca moth— 
behaviour which is essential to the biological end of repro- 
* See A. G. Mayer “On the Mating Instinct of Moths.” Ann. and 
Mag. of Nat. Hist., ser. 7, vol. v., Feb., 1900, p. 183. 
