colour, spotted with black; on which account they have been named Ermine and Leopard moths. Like the tiger-moths, to which they are nearly related, they are subject to great variety in their markings, even in the same species; of the common British species, S. menthastri, not fewer than eight well marked varieties have been described.
The wings of the male of S. acrea expand about two inches, those of the female two inches three quarters. Head, thorax, and upper wings of the male cream-coloured, the surface of the latter with numerous small black spots, five of which are placed in a regular row along the anterior border, and six on the external one; hinder wings entirely yellow, with a few black spots near the external edge and middle. The abdomen is yellow, with a row of black spots down the centre, and another on each side; the apex cream-coloured.
In the female all the wings are white, with numerous black spots, which are very variable in their distribution, but there is a marginal row on the hinder wings which does not exist in the other sex. The abdomen is coloured nearly as in the male; eyes and antennæ in both sexes black.
The caterpillar is said to be white when young, and to become nearly black when full grown, a transition to two extremes which is not common even among a race of creatures subject to great variation in regard to colour. In its intermediate stages, the prevailing hue is reddish-brown. When it has attained the period of its growth at which we
