Lepidoptera The Small White Butterfly – P. Rapa

This butterfly closely resembles the last species except in point of size. The male, represented on Butterfly PhotoPlate I (fig. 4), has a dark grey blotch at the tip of each fore wing, a round spot of the same colour beyond the centre of that wing, and another on the costal margin of the hind wing. The female may be distinguished by an additional spot near the anal angle of the fore wing.

Although this and the two other common butterflies (Brassica and Napi) that frequent our kitchen gardens are usually spoken of as ‘Whites,’ a glance at a few specimens will show that they are not really white at all, but exhibit delicate shades of cream and yellow, inclining sometimes to buff. The under surfaces are particularly noticeable in this respect, for here the hind wings and the tips of the fore wings display a very rich yellow.

The species we are now considering is also very variable both in its ground colour and the markings of the wings. The former is in some cases a really brilliant yellow; and the latter are in some cases entirely wanting.

Rapa is double-brooded, the first brood appearing in April and May, and the other in July and August.

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 (Tropaolum 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 larva 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 pupa may be found during the same seasons and in the same situations as those of Brassica. 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.