re very
bitter, or disagreeable or dangerous as food, still, in the number of
small green caterpillars which birds love, it would be continually
swallowed by mistake. If, on the other hand, it had a conspicuous and
peculiar color, its evil taste would serve to protect it, because the
birds would soon recognize and avoid it, as has been proved
experimentally. I have already alluded to a case of this among the
Hawk-moths, in a species which, feeding on euphorbia, with its bitter
milky juice, is very distasteful to birds, and is thus actually
protected by its bold and striking colors. The spots on our Elephant
Hawk-moth caterpillar do not admit of this explanation, because the
insect is quite good to eat--I mean, for birds. We must, therefore, if
possible, account for these spots in some other way. There can, I
think, be little doubt that Weissmann is right when he suggests that
the eye-spots actually protect the caterpillar, by frightening its
foes.

Every one must have observed that these large caterpillars--as, for
instance, that of the small Elephant Hawk-moth (Fig. 10)--have a sort
of uncanny poisonous appearance; that they suggest a small thick snake
or other evil beast, and the so-called "eyes" do much to increase the
deception. Moreover, the segment on which they are placed is swollen,
and the insect, when in danger, has the habit of retracting its head
and front segments, which gives it an additional resemblance to some
small reptile. That small birds are, as a matter of fact, afraid of
these caterpillars (which, however, I need not say, are in reality
altogether harmless), Weissmann has proved by actual experiment. He
put one of these caterpillars in a tray in which he was accustomed to
place seed for birds. Soon a little flock of sparrows and other small
birds assembled to feed as usual. One of them lit on the edge of this
tray, and was just going to hop in, when she spied the caterpillar.
Immediately she began bobbing her head up and down, but was afraid to
go nearer. Another joined her, and then another, until at last there
was a little company of ten or twelve birds, all looking on in
astonishment, but not one ventured into the tray; while one bird,
which lit in it unsuspectingly, beat a hasty retreat in evident alarm,
as soon as she perceived the caterpillar. After watching for some
time, Weissmann removed it, when the birds soon attacked the seeds.
Other caterpillars also are probably protected by their cu