The Orange-tip (Euchloë Cardamines)
This butterfly (Plate 17), as its name suggests, has a large patch of orange colour on the outer third of its white, or creamy white, fore wings, and the extreme tip is blackish; at least, this is so in the male. The female is without the orange patch, and this is replaced by a smaller one of blackish-grey. The lower portion of this patch is broken up by the ground colour, and by white spots on the outer margin and around the tips of the wings. The hind wings, in both sexes, appear to be dappled with greyish-green, and this is caused by the green marking on the under surface of the wings showing through. Some specimens, chiefly from Ireland, have all the wings in the male, and the hind wings in the female, distinctly tinged with yellow. The discal black spot varies in size and in shape; often it is roundish, and sometimes it is crescent-like. It is always larger in the female than in the male, and may be entirely absent in the latter sex; but this probably occurs very rarely. Usually the orange patch of the male extends very near to the inner angle of the wing, but sometimes it is continued through to this point. It ranges in colour from deep to pale orange, and occasionally to almost yellow. Small specimens, some not more than one inch and a quarter in expanse, occur from time to time. In these dwarfs the orange patch does not reach beyond the black discal spot, which in normal specimens it usually does. This small form has been considered a distinct species, and the name hesperidis has been proposed for it. Female specimens with splashes or streaks of the male colour on the upper or the under sides have been noted not infrequently; and more rarely specimens with one side entirely male and the other entirely female have been taken.
The egg (Plate 15), when freshly laid, is whitish, faintly tinged with greenish; it soon changes to yellow, and, later on, turns orange and then dark violet. When the latter colour appears, the little caterpillar may be expected to hatch out very shortly. The eggs are placed upright on the foot-stalks of the flowers, and may be readily found in June by searching the blossom-clusters of hedge-mustard or cuckoo-flower.
The caterpillar, when mature, is dull bluish-green, with raised dots and warts; from the former arise whitish hairs, and from the latter longer blackish hairs. There is a white line, or stripe, along the sides, and the underparts of the body are greener than the back. Both in colour and marking the caterpillar agrees so closely with the seed-pods of its food-plant that its detection is not always easy. A peculiarity in very young caterpillars of this species, and also those of some of the “Whites,” is, that the hairs are forked at the tips, and bear globules of moisture thereon (see figure and remarks on p. 3).
The caterpillars feed in June and July on lady’s smock or cuckoo-flower (Cardamine pratensis), charlock (Brassica sinapistrum), hedge-mustard (Sisymbrium officinale), garlic mustard (S. alliaria), rock-cress (Arabis), horseradish (Cochlearia armoracia), dame’s violet (Hesperis matronalis), watercress (Nasturtium officinale), etc.
The chrysalis, as will be seen from the figure (Plate 15), is curiously elongated, and tapers towards each end; the outline of the back is curved, and the wing-cases bulge out into an angle about the middle of the under side. The colour is pale grey or whitey-brown, sometimes with a strong rosy tinge; the back is speckled with brownish, and has an olive-grey dorsal line, and the veins of the wings are well defined. This stage lasts, as a rule, from August of one year until May of the following year. When the chrysalis is first formed, it is green, with the wing-cases brighter, and this colour is sometimes retained. It has been stated that the chrysalids assume the colour of their immediate surroundings, and this may be so; but all that I have had under observation were of the colours described above, although some were fastened to green stem, others to muslin, and others, again, to glass.
Towards the end of May and in June is the usual time for this butterfly to be on the wing. It has, however, been noticed as early as about the middle of April, and as late as the middle of July, and rarely in August and September. The specimens, seen in the last-mentioned months, may have represented a second brood, and, if so, a very unusual event. Possibly, however, they may have been specimens whose emergence had for some reason not understood, been retarded. There is at least one record of the insect remaining in the chrysalis for two winters.
Although generally distributed throughout England, Wales, and Ireland, and occurring in Scotland as far north as the Caledonian Canal, it seems to be more common in some districts than in others. Abroad, its range extends over Europe, and through Asia as far east as Amurland and China.