The Holly Blue (Cyaniris Argiolus)
About the beginning of the eighteenth century this butterfly (Plate 113) was known as the “Blue Speckt,” but Harris, in 1775, changed the name to the “Azure Blue.” The male is a pretty lilac-tinged blue, with a narrow black edging on the outer margin of the fore wings, often only in evidence towards the tip, and a narrow black line on the outer margin of the hind wings. The white fringes of the fore wings are distinctly marked with black at the ends of the veins. The female is of the same shade of blue, or sometimes much paler (var. clara, Tutt), with a broad blackish border on the outer margin of the fore wings extending along the front margin to about the middle; this border varies in width and seems to be wider in summer specimens than in those of the earlier flight; the discal mark on the fore wings is black, but this is sometimes very faint; there is a series of black dots on the outer margin of the wings.
Although the colour of the upper side is somewhat like that of the Common Blue, it should not be confused with that species, as the under side is very different both as regards the colour, which is bluish-white, and the arrangement of the black spots. On the outer margins of the wings in some specimens there are more or less distinct traces of blackish crescents.
There is no considerable variation in this species, but the spots on the under side are subject to slight modification in the matters of size and shape; the borders also vary in width, and in the female the blue area is thus sometimes much restricted. A gynandrous specimen has been recorded, in which the right side is male.
The egg (Plate 112) is described as whitish or bluish-green in colour.
The full-grown caterpillar has a blackish head, the body is bright yellowish-green with paler lines; eight rings from and including the second are crested with two ridges of humps, between which lies the sunk dorsal space; the whole skin of the body is velvety, with its surface thickly covered with yellowish warty granules, each bearing a minute bristly white hair. Sometimes the humps and the middle of the back are marked with rose-pink.
The chrysalis is pale brownish-ochreous with a thin blackish-brown line on the back of the brown freckled thorax; the body is marked with rather blotchy arrow-head dashes, and some larger dark brown blotches; the wing-cases are pale greyish freckled and outlined with brown, their surface is smooth and rather more glistening than the other parts, which are thickly studded with fine, short, brownish bristles. (Adapted from Buckler.)
The following is a brief summary of a paper by Mr. R. Adkin (Proc. S. Lond. Ent. and Nat. Hist. Soc. for 1896), in which he gives a most interesting account of the earlier stages of the second brood of this species.
At the time when the butterflies of the second brood are on the wing, the flower-buds of the ivy (Hedera helix) are still young, and form compact heads. The butterfly, having selected one of these heads, settles upon its top, closes her wings over her back, and bending her abdomen down and round underneath the buds, affixes an egg to the under side of one of the slender single bud-stalks. In about a week the eggs hatch. The young larva which in colour matches the buds very closely, rests on the bud-stalk with its anterior segments, which completely cover its head, pressed closely against the bud, and looks so exactly like a slight swelling of the upper part of the stalk as to make detection a matter of great difficulty, even with the aid of a fairly powerful lens. The larva is very sluggish in its habits, seldom leaving the head of the buds on which it is hatched, so long as sufficient food remains for its nourishment, or occasionally when about to change its skin. It appears to feed only at night, and its manner of feeding, which is the same throughout its life, is to eat a round hole through the outer shell of a bud, and pressing its head forward through it to clear out the soft inside of the bud. In from four to six weeks it is full-fed; it then quits the buds, and attaches itself by slender threads to a leaf, and in a few days becomes a pupa, in which state it passes the winter.
Normally the eggs of the spring butterflies are laid on the under side of the calyces of flower-buds of holly (Ilex). The caterpillars feed on the flower-buds and also on the young green berries. They are full grown in about a month, change to chrysalids, and the butterflies emerge in July and August. Among other pabula that have been mentioned are the flowers of dogwood (Cornus sanguinea), berry-bearing alder (Rhamnus frangula), and spindle (Euonymus europæus).
In confinement the caterpillars will eat young leaves of holly and probably of ivy also, but where flower-buds are available they prefer them and ignore the tender leaves.
The Rev. Gilbert Raynor, on May 18, 1901, observed a female deposit an egg on an unopened flower-bud of rhododendron in his garden; and he also mentions that he beat a number of the caterpillars of all sizes from holly during the first week of July in the same year.
Mr. Dennis reported that on October 9, 1902, all stages of the species were to be found at Earl’s Colne, Essex.
Butterflies of the first flight are usually to be seen in April and May, and of the second, which is perhaps only partial and may not be represented at all, in July and August. Specimens have been observed as early as the last week of March, and, as adverted to above, as late as October. For a few years in succession the species may become increasingly numerous, and then suddenly become quite scarce for a year or two. Most probably this is the result of favourable or unfavourable weather conditions.
The taller hollies, where these grow in gardens, open woody places, on hillsides, or even in hedgerows, are frequented by these butterflies in the spring; and the ivy-clad walls, etc., are their haunts in the summer.
The species is widely distributed, and often common, over the whole of the south of England and Wales. North of the Midlands, as well as in Ireland, it is more local, and occurs, I believe, only in the first brood. Possibly in the South of Ireland there may be a second brood. Barrett states that there is no reliable record for Scotland.
Abroad, its range extends throughout Europe and Northern Asia, except the Polar Regions, to China and Japan. It also occurs in North Africa.