Are birds easily deceived ?



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The idea of warning-colours seems to have been first suggested

to Darwin by Wallace (‘ Descent of Man,’ 2nd ed., p. 499) to account

for the existence of brilliantly coloured caterpillars which seemed to

be destitute of any other means of protection, excepting perhaps that

they might be distasteful; and he stated that the skin of caterpillars

was extremely tender, so that if a bird pecked one in order to sample

its flavour, it would infallibly die. I don’t admit either assumption.

The skin of some caterpillars is comparatively tender, of others it is

extremely tough, and I have known caterpillars which have been

injured to develop into moths in which there was only a slight imper¬

fection.


I believe that caterpillars striped black and yellow like wasps

(as that to which Darwin called Wallace’s attention) are usually

nauseous, and I think they are fairly thick-skinned; certainly the

insects they become are not easily killed. As a general rule I should

say that distasteful butterflies and moths, such as Parnassius, the

Danaids both of the Old and New Worlds, the Acrceids, the Zygcenids,

and some of the Arctiids among the moths are so little affected by

one hard pinch that a single attack by a bird would have no

permanent effect upon them. If all nasty butterflies were coloured

alike I could quite understand birds and beasts taking notice of their

hues ; but they are of all the colours in the rainbow ; there is nothing

distinctive about them.


The late Professor Packard, of the States, asserted that the hairs

and spines on caterpillars protected them against the attacks of their

enemies, but not only do many of the larger birds simply rub off the

hairs and then devour them, but the most hairy of our British

caterpillars, that of the common Tiger-moth, is more subject to

attacks from ichneumon-flies than any other caterpillar known to me.

Many of my birds ate the spiny caterpillars of the small tortoise¬

shell butterfly, some of them rubbing off the spines, but some

swallowing spines and all. Birds are not so foolish as to refuse good

food because it gives them a little trouble to prepare it.


When one reflects, one wonders what possible good it can do

to a species if it possesses warning colours in one stage to advertise

its nastiness, and in a later stage it ceases to be nasty ? Birds do

not say to themselves “ that gooseberry-moth came from a nasty



