The Pale Clouded Yellow (Colias hyale).
This usually scarce butterfly (Plate [21]) is of a primrose-yellow colour in the male, and, as a rule, almost white in the female; sometimes the latter sex is of the yellow male colour. The outer margin of the fore wings is broadly black in both sexes, but there are some more or less united spots of the ground colour in the black towards the tips of the wings, and below vein 3 the black is usually confined to the outer margin. There is a black spot near the middle of the wing, and some blackish dusting quite near the base of the wing. The hind wings have a pale orange central spot, sometimes two spots, and the blackish border on the outer margin is generally narrow, and often interrupted or broken up into spots. The fringes of all the wings are pinkish, as also are the antennæ. The egg is pearly yellowish-white when first laid; a few days later the top becomes transparent, white, and glassy, shading downwards into yellow, and then clear rosy orange; the base is pale, but less transparent than the top. It has a number of transverse ribs, ranging from nineteen to twenty-two. Before the caterpillar hatches out, the egg changes to a purplish leaden colour.
Pl. 18.
Wood White Butterfly.
Eggs, natural size and enlarged; caterpillar (after Buckler) and chrysalis.
