The Green Hairstreak (Callophrys Rubi)
Both sexes of this butterfly (Plate 96) are brown with a faint golden tinge above, and green on the under side. The male has a dark, or, when the plumules are dislodged, pale sexual mark, which is oval in shape, and placed at the upper corner of the discal cell in the fore wings. Occasionally there are some orange scales at the anal angle of the hind wings, and more rarely, and in the female, at the extremities of veins two and three also. On the under side of some specimens, chiefly from Northern localities, there is a transverse series of white dots across all the wings; more often these are confined to the hind wings, and sometimes they are almost or quite absent from all the wings. Now and then the under side of the hind wings is found to be brown in colour, and this change in colour has been ascribed to the action of moisture. The life-history is figured on Plate 97.
The egg is greenish, reticulated with paler or with whitish-green; the reticulation is somewhat rough on the side, but becomes finer towards and on the top, which has the centre hollowed. Laid on the petals of the common furze (Ulex europæus), and on leaves of rock-rose (Helianthemum chamæcistus).
The caterpillar feeds in June and July. It is pale green, with a darker line along the back, and yellow oblique stripes on the sides. Among the plants that it has been found upon, or is known to eat, are dyer’s greenweed (Genista tinctoria), needle furze (G. anglica), broom (Cytisus scoparius), dwarf furze (Ulex nanus), whortleberry (Vaccinium myrtillus); also the berries of buckthorn (Rhamnus), making holes through which the contents of the berry is extracted; buds of bramble (Rubus), and of dogwood (Cornus sanguinea), are also attacked in a similar way.
The chrysalis is clothed with tiny hairs, and when freshly formed is green in colour, but becomes purplish-brown after a time. It appears to be unattached to anything. I think, however, that there are generally a few strands of silk around or about it, but these are so easily broken when the chrysalids are removed that they escape observation. May and June are the months for the butterfly, which occurs in various kinds of situations, such as the outskirts of woods, high hedgerows, hill slopes, and boggy heaths. I once saw it in abundance about the entrance from Lynton to the Valley of Rocks. Its resemblance on the under side to the leaves on which it perches is as baffling to the collector as is the resting habit of the Grayling butterfly previously referred to. It seems to be pretty generally distributed throughout the kingdom, but is rather more local in Ireland than elsewhere, and it has not yet been recorded from the Orkney or Shetland Isles. Its range extends throughout the Palæarctic Region.