During these months the eggs may be seen in plenty on its numerous food plants, which include the cabbages and horse-radish of our gardens, also water-cress (Nasturtium officinale), rape (Brassica Napus), wild mustard (B. Sinapis), wild mignonette (Reseda lutea), and nasturtium (Tropæolum majus).
The eggs are conical in form—something like a sugar loaf, with ridges running from apex to base, and very delicate lines from ridge to ridge transversely.
The young larvæ often make their first meal of the shell, and then attack the food plant so voraciously that they are fully grown in about three or four weeks. In colour they are of a beautiful glaucous green, hardly distinguishable at times from the leaves on which they rest. A yellow stripe runs along the middle of the back, and lines of yellow spots adorn the sides; and the whole body is covered with very short hairs, each one arising from a minute warty projection.
The pupæ may be found during the same seasons and in the same situations as those of Brassicæ. They are very variable in colour. Some are of a very pale grey or putty colour, some are decidedly brown, and others of a greenish tinge; and they are often spotted and striped with dark grey or black.
The Green-veined White (P. Napi)
A non-observant beginner at entomological work may easily mistake this insect for the last species, for the ground colour and markings are very similar, even to the features by which the sexes are distinguished from each other; but an inspection of the under surface will give a ready means of identification, for here the wing rays are bordered with black scales which, by contrast with the
rich yellow around them, often appear of a greenish hue. The butterfly receives its popular name from this circumstance.
A careful observer, however, will readily find distinguishing marks on the upper side, for here also the chief 'veins' are more or less accompanied with black scales, especially the extremities of those of the fore wings, where little triangular blotches are often distinctly formed; and the dark veining of the under surface of the hind wings frequently shows through. The under side of this insect is shown on [Plate I] (fig. 5).
This butterfly is not so abundant as the two preceding, but is widely distributed throughout England, and is in most parts decidedly plentiful.
The first brood (for it also is double-brooded) appears during April and May, and the second in July and August.