Let us consider the ontogeny of these different forms of markings, beginning with the eye-spots. It appears that these develop from a sub-dorsal stripe, which appears in the young caterpillar in the second stage of its life, and from it, in the course of the further development, two pairs of large eye-spots are formed. Even in the young caterpillar, scarcely one centimetre in length (Fig. 116), it can be observed that the fine, white sub-dorsal line takes a slight curve upwards on the fourth and fifth segments (_C_), and on the lower edge of these curves a black line is laid down (_D_). This is then continued to the upper side (_E_), and encloses the piece of the sub-dorsal stripe (_F_ and _G_), and thus there arises a white-centred, black-framed spot which only requires to grow and to differentiate a blackish shadow-centre, the pupil (_G_), to give the impression of a large eye. This occurs as the caterpillar goes on growing, and after the fourth moult or ecdysis the eyes have already some effect, as the animal is six centimetres in length, but they become even more perfect in the fifth and last stage. During this development of the eye-spot the sub-dorsal stripe disappears completely from the greater part of the caterpillar, persisting only on the first three segments (Fig. 116, _B-F_). [Illustration: FIG. 116. Development of the eye-spots in the caterpillar of the Elephant Hawk-moth (_Chærocampa elpenor_). _A_, Stage I, still without marking, simply green. _B_, Stage II, with sub-dorsal stripe (_sbd_). _C_, sub-dorsal line somewhat later, with the first hint of the eye-spot (_Au_) on segments 4 and 5. _D_, eye-spots in Stage III of the caterpillar, somewhat further developed than in _E_, the third stage. _F_, Stage IV. _G_, the anterior eye-spot at the same stage.]