ation.

There are certain ants of the Amazons which present the curious instinct
of cutting off leaves from trees, and carrying them like banners over
their heads to the hive, as represented in Fig. 116, B, where one ant is
shown without a leaf, and the others each with a leaf. Their object in
thus collecting leaves is probably that of growing a fungus upon the
"soil" which is furnished by the leaves when decomposing. But, be this
as it may[39], the only point we are now concerned with is the
appearance which these ants present when engaged in their habitual
operation of carrying leaves. For it has been recently observed by Mr.
W. L. Sclater, that in the localities where these hymenopterous insects
occur, there occurs also a _homopterous_ insect which mimics the ant,
leaf and all, in a wonderfully deceptive manner. The leaf is imitated by
the thin flattened body of the insect, "which in its dorsal aspect is so
compressed laterally that it is no thicker than a leaf, and terminates
in a sharp jagged edge." The colour is exactly the same as that of a
leaf, and the brown legs show themselves beneath the green body in just
the same way as those of the ant show themselves beneath the leaf. So
that both the form and the colouring of the homopterous insect has been
brought to resemble, with singular exactness, those belonging to a
different order of insect, when the latter is engaged in its peculiar
avocation. A glance at the figure is enough to show the means employed
and the result attained. In A, an ant and its mimic are represented as
about 2-1/2 times their natural size, and both proceeding in the same
direction. It ought to be mentioned, however, that in reality the margin
of the leaf is seldom allowed to retain its natural serrations as here
depicted: the ants usually gnaw the edge of the real leaf, so that the
margin of the false one bears an even closer resemblance to it than the
illustration represents. B is a drawing from life of a group of five
ants carrying leaves, and their mimic walking beside them[40].

[39] For a full account of this instinct and its probable purpose,
see _Animal Intelligence_, pp. 93-6.

[40] Both drawings are reproduced from Mr. Poulton's paper upon the
subject (_Proc. Zool. Soc._, June 16, 1891).

[Illustration: FIG. 116 PROTECTIVE MIMICRY]

CHAPTER IX.

CRITICISMS OF THE THEORY OF NATURAL SELECTION.

I will now proceed to consider the various objections an