Larger Image
Pl. 21.
Pale Clouded Yellow.
1, 2 male; 3, 4 female.
When it occurs in this country the butterfly should be looked for in clover and lucerne fields.
Common throughout the Palæarctic Region. It is probably a species of Eastern origin, but with a tendency to spread westward.
The Clouded Yellow (Colias edusa).
In its typical colouring—orange with broad black borders—this butterfly (Plate [22]) will be recognized the first time it is seen. Both sexes have a black spot about the centre of the fore wings, and a deep orange spot near the middle of the hind wings—the latter is subject to variation in size and shape. The female usually has the black borders spotted with yellow, but in some examples these spots are almost (Plate [24,] Fig. [1]) or quite absent. Another form of the female, known as var. helice (Plate [24,] Fig. [2]), has the orange colour replaced by yellowish-white, and in some years is not altogether uncommon. Between this yellowish-white at one end of the colour range and the typical orange at the other, specimens showing all the intermediate shades have been obtained, chiefly by rearing the butterflies from eggs laid by a female helice. One of these intergrades will be seen on Plate [24,] Fig. [3]. The males vary, especially bred ones, from "deep rich orange to the palest chrome yellow; the marginal bands also vary in width; in many examples the yellow nervules run through the borders of all the wings. A large proportion of the males have the hind wings shot with a beautiful amethystine blue" (Frohawk).
The egg (Plate [23]) is oval, tapering towards each end, very pale yellowish in colour at first, but afterwards becoming darker yellow, and then pink. The eggs are laid, as shown in the figure, on the upper side of a leaf of clover or lucerne, sometimes singly, but often in small batches.
The caterpillar when full grown is deep green with minute black dots, from which fine hairs arise, and a pink-marked yellow, or whitish, spiracular line. The head is also green, rather downy, and small in size. When first hatched the caterpillar is brownish, but soon changes to greenish. It feeds on clover (Trifolium), trefoil (Lotus), melilot (Melilotus), etc., in June and again in September or October.