The Peacock (Vanessa Io)
Unlike the last species referred to, this handsome butterfly is more frequently seen in the autumn than after hibernation. It is not likely to be mistaken for any other kind, for on its brownish-red velvety wings it bears its own particular badge, the “peacock eyes.” The marks on the hind wings are more like the “eyes” on the tail feathers of the peacock than are those on the fore wings, and the brownish-red on these wings is confined to a large patch below the eye-mark, the remainder being blackish, powdered with yellow scales on the basal area. Some specimens have a blue spot below the “eye” on the hind wings, and the name cyanosticta has been proposed for this form by Raynor. The under side is blackish, with a steely sheen, and crossed by irregular black lines; the fore wings are tinged with brown on the inner area, and the central dot and a series of dots beyond are ochreous; the hind wings have an ochreous central dot.
In a state of nature the butterfly seems little given to variation. In rearing from the caterpillar, however, some curious aberrations occasionally crop up. In my early days of collecting I raised a number of specimens from caterpillars selected from a large brood; every one of these butterflies was of a dull brownish colour and had a greasy semi-transparent appearance. I regret to add that I set them all at liberty as they did not come up to my, then, standard of what a Peacock butterfly should be. Now and then specimens are bred from collected caterpillars, in which the eye spots are represented by a broad white cloud-like suffusion on the fore wings, and by a pale roundish patch on the hind wings; in conjunction with this the black costal spots of the fore wings are all more or less united (see Plate 41). This extreme variety is known in the vernacular as the “Blind Peacock,” and as ab. belisaria in science; between it and the typical form there are all kinds of intermediate modifications, and one of these is also shown on the plate referred to. It may be interesting to remark that similar varieties have been produced by subjecting the chrysalids at a particular period to a very low temperature. Readers who may wish to know more about “Temperature Experiments” are referred to a pamphlet on the subject by Dr. Max Standfuss.
The egg, an enlarged figure of which will be found on Plate 39, is olive green in colour, and has eight ribs, which start just above the base and turn over the top. The eggs are laid in April or May in batches on the upper part of nettle plants and under the young leaves.
The mature caterpillar is velvety black with white dots, and the divisions between the rings of the body are well marked. The spines are black and rather glossy, and besides this clothing, the body is also provided with short hair which gives the velvety appearance. The head and a plate on the next ring, also the legs, are shining black; the prolegs are blackish, tipped with yellowish. When quite young they are greenish-grey, and although hairy are without spines. The caterpillars usually feed in companies in June and July on the common stinging nettle. They have also been found on hop. Once or twice I have reared caterpillars of this butterfly, and also those of the Small Tortoiseshell and the Red Admiral, on hop, but the result has been disappointing, as the specimens produced were always small in size. The individuals for these experiments were obtained from nettle, and were generally about half grown at the time they were put on the hop diet.
The chrysalis is figured on Plate 39. Its colour may be pale greenish, greyish, pale brown, or brownish-grey, but is usually stippled with blackish, especially the antennæ and the outline of the wing-cases. Some of the points on the thorax and the ring, or rings, next to it have a metallic lustre. Two chrysalids among those resulting from my hop-fed caterpillars were more or less suffused with the metallic sheen. It does not seem to be very clearly known where the caterpillars retire to for pupation. Those that I have found have been under a tent-like arrangement of the lower nettle leaves. In confinement, however, I have noted that in a roomy cage they all go to one end of it and suspend themselves from the roof; in a large flower-pot they crowd together in much the same way.
The butterfly is on the wing in August and September, and frequents all and every kind of ground where flowering plants, especially the taller kinds, are available; clover fields are attractive, and so also are orchards. It passes the winter in some hollow tree trunk, wood stack, or possibly buildings of some kind, and in the spring it again comes forth. March and April are the usual months for its reappearance, but in 1900 it was seen flying over the snow on February 17. The time last mentioned is probably an unusual one, but it is interesting to note that a very similar observation was made by Harris, who in 1778 wrote in his remarks on this butterfly, “I have seen them flying in February, when the snow has been on the ground.”
Usually the Peacock butterfly assumes the perfect state but once in the year. There is, however, a record of half-grown caterpillars being found in September, and that these produced butterflies in due course.
Although not always abundant, the butterfly is to be, or has been, found in almost every part of the kingdom, excepting perhaps north of the Caledonian Canal in Scotland. Around Bishop Auckland and in other parts of the county of Durham, and also in Northumberland, it was common some forty years ago, but it seems to be hardly ever seen there now. The same applies to other northern localities where it was once plentiful. Its distribution includes the whole of Europe, Asia Minor, Siberia, Amurland, Corea, and Japan.