Among Lepidoptera, too, eye-spots often occur on the wings, and to some extent, at least, they have in this case also the significance of warning marks. Take, for instance, the large blue and black eye-spots on the posterior wings of the eyed hawk-moth (_Smerinthus ocellatus_). When the insect is sitting quietly the two spots are not visible, as they are covered by the anterior wings, but as soon as the creature is alarmed it spreads all four wings, and now both eyes stand boldly out on the red posterior wings and alarm the assailant, as they give the impression of the head of a much larger animal (see Fig. 5). There are also eye-like spots which have not this significance and effect, as, for instance, the 'eye-spots' on the train-feathers of the peacock and the Argus pheasant, or the little eye-like spots on the under surface of many diurnal butterflies. In the first case, it is a matter of decoration; in the second, perhaps of the mimicry of dewdrops, which increases still further the resemblance to a withered leaf; but there are undoubtedly many cases in which the eye-spots serve as means of frightening off enemies, and these cases are especially common among butterflies. [Illustration: FIG. 5. The Eyed Hawk-moth in its 'terrifying attitude.'] Such warning marks are in no way contradictory to the sympathetic colouring of the rest of the body, and indeed we usually find them in combination with it. In some cases the eye-spot, though very conspicuous, is covered, as in the eyed hawk-moth, when at rest, by the sympathetically coloured parts--in this instance the anterior wings. In other cases eye-spots of considerable size lie clearly exposed, but exhibit the same sympathetic colours as the whole of the rest of the wing-surface. In this case they do not interfere with the protective influence of general colouring, because they are only visible from a very short distance. This is the case in the large _Caligo_ species of South America, which only fly for a short time in the early morning and in the evening, remaining concealed throughout the day in dark shadowy places, where the mingled colouring of brown, grey, yellow, and black on the under surfaces of the wings prevents their being recognized from a distance as butterflies at all. But even the best sympathetic colouring is not an absolute protection, and when the insect is discovered by an enemy near at hand, the terrifying mark, a large deep-black spot on the posterior wing, comes into effect, and scares the assailant away. [Illustration: FIG. 6. Under surface of the wings of _Caligo_.]