The Wood White (Leucophasia Sinapis)
The graceful little butterfly figured on Plate 19 is creamy white, with a rather square black or blackish spot on the tip of the fore wings of the male. In the female the spot is reduced to some blackish scales on and between the veins. Occasionally there is a second brood in the year, and the specimens of this flight have smaller and rounder black spots in the males, and almost none at all in the females. Specimens of the female sex entirely devoid of black marking are referable to var. erysimi (see fourth figure in second row, Plate 16). Series of each brood are shown on Plate 16, which is reproduced from a photograph by Mr. Hamm. The lower specimen in each series has been reversed to show the seasonal variation of the under side. The row of specimens on the left are of the first brood, and the second and last examples in this series show the characters of var. lathyri—black tips to the fore wings, and dusky band-like shades on the hind wings; the under sides of the hind wings dull greenish—to which form a good many of our spring specimens belong. The specimens of the second generation are referable to var. diniensis. The species is sometimes referred to Leptosia, Hüb.
The egg, which is figured on Plate 18, is yellowish-white in colour; it is ribbed, and rather glassy in appearance. The caterpillars have been known to hatch out about a week after the eggs were laid.
The caterpillar when full grown is, according to Hellins, “a beautiful green, the front segments minutely dotted with black; dorsal line darker green, edged with yellowish-green; spiracular line distinct, of a fine clear yellow, edged above with darker green; spiracles indistinguishable.” The chrysalis in shape is something like that of the last species, but the back is not curved, and the ends are less tapered. The colour is a “lovely delicate green; the abdomen rather yellowish; just in the spiracular region there runs all round the body a stout pink rib, enclosing the greenish spiracles; from this a strong pink line branches off, bordering the outer edge of the wing-case, and the nervures of the wings themselves are delicately outlined in pink” (Hellins). Sometimes the chrysalids are green without marking.
Mr. A.M. Montgomery, who on one occasion had four batches of eggs, and the subsequent caterpillars, under observation, states that the caterpillars hatched about June 2 from eggs laid about May 22. Pupation took place about July 3, and, except from one batch that remained for the winter in the chrysalids, the butterflies emerged between July 16 and 22. The food-plant in this case was bird’s-foot trefoil (Lotus corniculatus). The yellow pea (Lathyrus pratensis) is a favourite pabulum, but the caterpillar will also eat a vetch (Vicia cracca), and probably many other plants belonging to the order Leguminosæ. Caterpillars from the July butterflies would feed in August and September.
This fragile-looking little species is somewhat local, but is not altogether uncommon in some of its particular haunts. As its English name implies, the butterfly is fond of the woods, or, perhaps, is rather more partial to their shady rides and margins. On dull or wet days, it settles on the under side of a leaf. The first brood is on the wing in May, and the second—when this occurs, which is not every year—in July and August. In Ireland, where it is abundant in the south and west, there seems to be only one flight, and this is in June. It may be well to remember that this butterfly does not like the pill-box, and will not settle down quietly therein.
Possibly the Wood White had a much more general distribution in England at one time than it now seems to have. It was not uncommon in parts of Sussex some years ago, but there appears to be no record of its occurrence there now. It is certainly much scarcer in the New Forest than it used to be. However, it is still to be found, no doubt, in many parts of England and Wales, but chiefly perhaps in the counties of Berkshire, Devonshire, Cornwall, Worcestershire, Herefordshire, Lancashire, and Cumberland. Also in the south and west of Ireland. It occurs throughout Europe, Western and Central Asia, and its range extends eastwards through Siberia, Amurland, China, and Corea to Japan.