This pretty butterfly, by far the commonest of the Hairstreaks, though comparatively very small, reminds one forcibly of the noble Purple Emperor. Its haunts are the same oak woods, and its upper surface, though only a dull dark brown in certain lights, exhibits the same imperial purple reflections when viewed at certain angles. The purple of the male extends over the whole of the wings, but that of the female is confined to a V-shaped patch at the base of the fore wings. In the latter case, however, the purple is much richer than in the male sex.
The under side ([Plate VI], fig. 6) is coloured with a delicate grey ground, adorned with a white streak on each wing, and a couple of orange spots near the anal angle of the hind wings.
This species is very widely distributed, being common in oak woods in most parts of England, and also in many parts of Scotland and Ireland. It flies around the branches of the trees, and often disappoints the collector by keeping far beyond the reach of his net.
Those in search of this pretty insect should ramble in oak woods, preferably in the south of England, during July and August. The eggs may be found glued to the twigs throughout the winter, and the larvæ may be beaten from the branches of the oak in June.
The colour of the caterpillar is brownish or pinkish green, with a row of V-shaped marks down the back.
The chrysalis is of a brown colour, short and thick, and may be found either attached to oak leaves, or under the surface of the earth at the foot of the tree on which the caterpillar fed.
The Green Hairstreak (Thecla Rubi)
Next to Quercus, this is the most plentiful of the genus. It frequents woods and heaths in nearly every county in England, and is also found in parts of Scotland and Ireland. It is peculiar among British butterflies as being the only one that exhibits a bright green colour. It also differs from the other Hairstreaks in two important particulars, for the hind wings, though angled at the hind margin, are not 'tailed,' and the characteristic hairstreak which gives the popular name to the genus is here represented only by a series of white dots across the wings, or, in some cases, by one or two dots on the hind wings only.