The White Admiral (Limenitis Sibylla)
The “White Admirable Butterfly,” as it was called by some of the older English entomologists, needs only to be seen to be at once recognized (Plate 33). The white markings on its blackish wings are somewhat similar to those of the Purple Emperor. As in that butterfly, so, too, in this, the most beautiful ornamentation is found on the under side. The shape of the wing is, however, very different in the two butterflies, and there is no probability of confusing one with the other. A somewhat uncommon form is shown on Plate 31 (also kindly loaned by Mr. Sabine); this is var. nigrina. Intermediates also occur, but these, too, are also rather rare. The eggs, which I have not seen, are stated to hatch in about fourteen days, and are laid in July. They have been described as pale green in colour, and of the shape of an orange, but flatter at the base and top.
The caterpillar (Plate 30) when full grown is dark green on the back and lighter on the sides, roughened with yellow dots, and with a yellow-marked white line above the feet. The bristly spines are reddish with pinkish tips, and those on the second, third, fifth, tenth, and eleventh rings are longer than the others. The first ring seems to be without spines, but the brownish head is set with short ones, two on the crown being rather longer and blacker than the others, and are inclined backwards.
In the autumn, when still quite tiny, it constructs a winter retreat (hibernaculum) (Plate 30) by fastening a growing leaf of sallow to a twig with silken threads, and then, using more silk, it draws the edges of the leaf together, and so forms a secure chamber wherein it can rest until the following spring, when it quits the domicile and sets to work on the tender foliage around it. At this time the caterpillar is brownish in colour. The chrysalis is of the remarkable shape shown on the plate. It is brownish, with purplish or olive tinge; behind the rounded hump there is a patch of bright green, and above the wing-cases a beautiful golden sheen. There are also other metallic spots and dots on various parts. Altogether, it is one of the prettiest of British butterfly chrysalids.
I am tempted here to quote Buckler’s excellent description of the pupation of this species, as it will serve to show the remarkable method by which caterpillars are able to perform a seemingly impossible feat; that is, to get absolutely free of the old skin whilst hanging head downwards from the silken pad or button to which they attach themselves by the anal claspers when preparing to pupate.
“When full fed the larva becomes rapidly paler, and then suspends itself by the anal prolegs to a stem of the honeysuckle or other surface, and hangs with its body downwards in a sinuous curve, with its head bent a little upwards, facing the abdomen; it then remains motionless for three days, becoming whitish on the abdomen, and remaining very pale green on the thoracic segments. In the course of the third day the creature seems to wake up, unbends its head, swings itself to and fro a few times, then stretches itself downwards in a long attenuated line, which causes a rupture of the skin close to the head; the skin then is seen slowly to ascend, exposing the bare and soft shining parts below, from which a flat and forked pair of horns grow out perceptibly as one beholds this wonderful process; the skin continues to glide slowly upwards, and as the soft parts become exposed, they are seen to swell out laterally, and to assume the very singular projections so characteristic of this chrysalis, the skin of the old head gliding up the belly marks the progress of the disclosure, as the colour of the old and new surfaces is at this time alike, the new being, however, rather more shining and transparent. Occasionally during the bulging out of the soft parts, a kind of convulsive heave or two occurs, but otherwise it remains still until the creature is uncovered as far as the ninth or tenth segment; it then curves its anal extremity by a sudden twist laterally, and in a moment dexterously withdraws the tip of the anal segment from the larval prolegs by an opening on the back of the skin at that part. At this critical moment one has time to see that the naked shining point is furnished with black hooks, and to apprehend a fall; but in another moment the pupa has forcibly pressed the curved tip with its hooks against the stem close to the previous attachment of the anal prolegs, and now it is strongly and firmly fixed. The creature now seems endowed with wonderful power and vigour; it swings boldly to and fro, and undulates itself as if to gain longer swings, when presently the old skin that remains is seen to burst away and fall off, the chrysalis gradually becoming quiescent, the entire metamorphosis, from the first waking to the last movement, occupying nearly seven minutes. In sixteen days the perfect insect emerged.”
Linnæus in 1767 wrote of the sexes of this butterfly as sibylla, or rather sibilla, and camilla, but, as Kirby points out, three years earlier the same author had given the butterfly the name camilla. It is probable, therefore, that the latter name will have to be adopted for our butterfly. Certain it is that the older British authors—Donovan, Haworth, Stephens, etc., knew our species as camilla. The species known on the Continent as camilla, and which, owing to the confusion of names has been supposed to be British, will have to be called drusilla, according to Kirby.
This species seems to be pretty much restricted to the southern and eastern counties of England. In the New Forest, Hampshire, it is often exceedingly abundant in July. So long ago as 1695 the butterfly was known to occur in Essex, and the species is found in some woods in that county at the present time. It has, however, quite disappeared from several woodland localities in Kent and Sussex, where it formerly occurred. It has been recorded from Shropshire and also from Worcestershire, but both these counties appear to be beyond the normal range of the species.
Almost all writers on our butterflies, from Haworth downwards, have commented on the graceful flight of the White Admiral as it skims aloft and alow through the woodland glades. This elegance of motion is still retained even when the wings become sadly torn and frayed, probably by contact with twigs and thorns.
Widely distributed throughout Central Europe. It is also found in Amurland, Corea, and Japan.