The chrysalis is yellowish-green above, somewhat paler below; the wing-cases are rather deeper in tint than the thorax and back, and have a central black speck and a row of slender marks at the edges. The body is marked with a splash of reddish and tiny black dots on the under side. The beak-like projection from the head is dark green above and yellow beneath.
The figures of the caterpillar and the chrysalis are taken from Buckler's "Larvæ of British Butterflies," and the descriptions of these stages by the same author have been followed.
The Clouded Yellow has a great fancy for clover or lucerne fields, and should be looked for in such places in August and September. It is not very difficult to rear from the egg, so that if a female is captured in August (the spring ones should not be taken), it would be a good plan to try to induce her to lay some eggs. The best method to succeed in this is to pot up a growing plant of clover, and over this place a glass cylinder with a muslin cover. (See further directions in the Introduction, page 28.)
This butterfly, which was known, to the earliest English authors as the "Saffron" or "Spotted Saffron," has always, no doubt, been erratic and uncertain in its appearance in this country, sometimes becoming increasingly abundant for three, four, or even five years in succession, and then scarce or entirely absent for similar periods. The most recent years of plenty, or when it was fairly common, were 1877, "the great Edusa year," 1892, 1893, 1894, 1895, 1899, 1900, and 1902. In some of these years the Pale Clouded Yellow was also common.
In some of the warmer countries that this butterfly inhabits it has certainly three, and possibly four, broods in the year. It is therefore conceivable that at times its increase in numbers may become very great in some particular area. At such times swarms of the surplus butterfly population set out to seek fresh fields and pastures new. Some portion of these flights reach our country from time to time, and this probably always occurs in the spring of the year. The weather conditions being favourable, the offspring of the visitors put in a welcome appearance in the autumn, and not only gladden the heart of the entomologist, but add a charm to the countryside which every one can appreciate.
The butterfly has probably occurred, at some time or other, in almost every county in England and Wales, Ireland and Scotland, extending even to the Orkney Islands (1877).
Its home appears to be in North Africa and South Europe, whence it spreads over the greater part of Europe and Western Asia.
Note.—According to Kirby, this butterfly should be called Eurymus hyale, Linn., and the Pale Clouded Yellow be known as Eurymus kirbyi, Lewis.