Lepidoptera The Green-veined White Butterfly – 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.
The eggs are very similar to those of Rapa, resembling ribbed and striated sugar loaves; and the larva are of the same rich glaucous green, but may be identified by the black spiracles surrounded by yellow rings. In our gardens we may find both eggs and larva on mignonette and horse-radish; the other food plants of this species include the water-cress (Nasturtium officinale), winter cress (Barbarea vulgaris), rape (Brassica Napus), cuckoo-flower (Cardamine pratensis), and Jack-by-the-hedge (Sisymbrium Alliaria).
The pupa is greenish, and marked with small black dots.