the thick herbage and dry sticks and leaves, near the ground, and it is obvious that under such circumstances the brown Colors really becomes a protection. It might indeed be argued that the caterpillars, having become brown, concealed themselves on the ground, and that we were reversing the state of things. But this is not so, because, while we may say as a general rule that large caterpillars feed by night and lie concealed by day, it is by no means always the case that they are brown; some of them still retaining the green Colors. We may then conclude that the habit of concealing themselves by day came first, and that the brown Colors is a later adaptation.