The egg. If the under sides of the leaves of buckthorn (_Rhamnus catharticus_) or of the berry-bearing alder (_R. frangula_) are examined in May or June, the eggs of this butterfly may be found thereon. They are often placed on a rib of the leaf, but sometimes they are laid as shown in the illustration (Plate 25). At first the colour is pale greenish and rather glossy, but it soon changes to yellowish, and later on, when the caterpillar has formed inside, to a dull purplish-grey. The caterpillar when full grown is green, merging into bluish-green on the sides, thickly powdered with shining black specks. There is a pale line on each side below the spiracles. It feeds in June and July on both kinds of buckthorn, and will generally be found resting along the main rib of a leaf. [Illustration: _Pl._ 22. =Clouded Yellow.= 1, 3 _male_; 2, 4 _female_.] [Illustration: _Pl._ 23. =Clouded Yellow.= _Eggs, natural size and enlarged; caterpillar and chrysalis._] The chrysalis is bluish-green in colour and of a curious shape. The sharp yellowish and brown beak-like projection in front and raised brownish bases of the wing-covers, together with the humped thorax, somewhat resemble a bird's head when seen from the front. Then, again, the enlarged wing-cases, which are rather greener than the other parts, in conjunction with the general outline, give a very good imitation of a curled leaf. The butterfly is very constant as regards colour and marking, but occasionally the fore wings may be more or less suffused with orange, and in this respect assumes the coloration of the South European species known as _G. cleopatra_. The attempt has been made to establish the last-named butterfly in Ireland, but the experiment seems to have been only partially successful. Sometimes female specimens are found to have splashes of the male colour on their wings. Occasionally their colour is intermediate between their own proper tint and that of the male, and more rarely the wings on one side may be yellow, as in the male, while those on the other side are greenish, as in the female. Such specimens are termed gynandrous examples, and sometimes hermaphrodites. The latter, however, is not correct. An unusual variation of the butterfly is shown on Plate 27. This has large oval pale brownish-orange marks on the under side of the wings. It was taken in the New Forest.