The above, I believe, is the best example known of a butterfly that escapes its enemies by looking like a leaf, or any other inanimate object; but there are others where the take-in is of a still more curious and unexpected kind. Certain butterflies have bitter juices in their bodies, and for this reason are let alone by birds and other enemies. As a consequence, other butterflies belonging to quite different families, have taken to mimicking them—just as if _they_ were leaves or sticks or grasses—so that, being mistaken for them, they are let alone too. If they were not so mistaken, they would be eaten at once—or at least whenever they could be caught—for their juices are very nice indeed. What seems still more extraordinary is that, in some cases, the nasty butterfly is mimicked only by the female of the nice one, and not by the male. Thus there is a butterfly in Africa, the male of which is a beautiful swallow-tail, but the female has no tails to her wings, and both in shape and colouring she is just like another butterfly, not nearly so handsome, and which is not a swallow-tail at all. What can be the reason of this? What can account for this favouritism in Nature?—for that is what it seems like. Why should only the nice-tasting female be protected, and not the equally nice-tasting male? But the male, it appears, can fly faster, and he is not bothered by having to lay eggs, like the female. The female, with eggs in her body, is heavier than he, and whilst she is laying them she has to sit still. This is the explanation generally given for a fact so remarkable. I confess that I don’t feel quite satisfied with it, but it is difficult to think of a better one. At any rate, there are the facts. Butterflies mimic each other, and pretend to belong to families which they really don’t belong to—just as adventurers do. But it may be said, how can one tell which is which, or, if two butterflies look exactly alike, how can we tell that they do belong to two families, and not to one and the same? But if one dissects a leaf-, or a walking-stick-insect, one does not find that it is like a leaf, or a piece of twig, inside, and just in the same way, though the difference is not so great, the two butterflies that look so much alike, are found to differ, on dissection. The internal organs of the mimicking kind have not been changed in the same way that its colouring and shape have been—for that would have done it no good—and then, again, it is not quite exactly like the other one; there is some difference, a little more, perhaps, than that between Tweedledum and Tweedledee, which would be enough for an entomologist, when he had the two on a table, to be able to tell.