The Brown Hairstreak (Zephyrus Betulæ)
The butterfly is represented on Plate 94, Figs. 1-3. The male is blackish-brown with a faint greyish tinge, and there is a conspicuous black bar at the end of the discal cell of the fore wing, followed by a pale cloud; there are two orange marks at the anal angle of the hind wings. The female is blackish-brown, and has the black bar at end of the cell, and an orange band beyond; there are usually three orange marks on the hind wings at the anal angle, but sometimes there are only two. The under side of the male is ochreous, but that of the female is more orange; the fore wings have the black bar edged on each side with white, and there is a white-edged, brownish triangular streak beyond, the outer margin is tinged with reddish; on the hind wings there are two white irregular lines and the space between them is brownish, the outer margin is reddish, becoming broadly so towards the anal angle, where there is a black spot. Variation is not of a very striking character. The shade following the black bar at end of the discal cell on the fore wings in the male is sometimes yellowish tinged, not infrequently fairly large, and with two smaller spots below it. More rarely all three spots are distinctly ochreous-yellow (var. spinosæ, Gerhard). A similar aberration, but with the marks white instead of yellow, has been named pallida, Tutt. The orange band in the female varies in width and in length; occasionally it extends well below vein 2, and into the discal cell within the black bar. I have one specimen in which the band is broken up into three parts, and the upper one of these is but little wider than the same spot in var. spinosæ, the other two being almost exactly of the same size as in that variety.
The life-history is figured on Plate 95—the lower set of figures.
The egg is described by Newman “as a depressed sphere and white,” and he states, “it is attached to the twigs of blackthorn (Prunus spinosa) in the autumn, often as late as the end of September or beginning of October; it is not hatched until the spring.”
The caterpillar is bright pale green, and the lines on the back and sides are yellowish, as also are the oblique streaks on the sides and the border of the ridge above the feet. There are some bristles along the ridge on the back and also on that above the feet. It feeds on blackthorn in May and June, and will eat the foliage of almost any kind of plum. I have reared fine specimens from caterpillars which fed on greengage.
The chrysalis is pale reddish-brown with a dark line down the middle of the back and some pale oblique streaks on each side; the wing-cases are freckled with darker brown. Barrett, quoting Fenn, says, “Suspended by the tail and a silken girth to the stem of the food-plant close to the ground.” Those that I have seen pupated on or under leaves, and so far as I could observe without any girth, and certainly not suspended.
Nearly two hundred years ago the male of this butterfly was known as the Brown Hairstreak, whilst the female was called the Golden Hairstreak. The caterpillar seems to have been observed in quite early times. It has always been a local species, and although it appears to frequent hedgerows occasionally, its haunts generally are open grounds in the neighbourhood of woods, where blackthorn or sloe is plentiful. August and September are the months for the butterfly, but it does not seem to be very often observed on the wing, even in places where the caterpillars are known to occur. When seen it is generally high up on, or around, some oak tree. Occasionally, however, it visits the bramble blossoms, and at such times becomes a fairly easy prey. The caterpillar is obtained by beating sloe bushes.
Barrett, who seems to have worked out its distribution in England and Wales pretty closely, remarks, “In the eastern counties it has been taken occasionally in Norfolk and Suffolk, more frequently in Essex, where, in Epping Forest, it has been fairly common; also in Cambridgeshire, Huntingdonshire, and Northamptonshire, in some plenty. In very few localities in Kent, Sussex, Hants, and Dorset; rarely in Gloucestershire, and possibly Somerset; but found in many Devonshire localities, especially in the sheltered valleys around the Dartmoor range, and in the charmingly wooded districts about Axminster and Sidmouth; becoming common towards Dartmouth. It has also been found commonly near Marlborough, Wilts, and plentifully in some parts of North Wales; apparently rare in South Wales, but certainly existing in some parts of the wooded districts skirting Milford Haven. Also recorded from Worcestershire, and Cannock Chase in Staffordshire; and northward in the favoured districts of Grange and Silverdale in North Lancashire, and Witherslack in Westmoreland.” As Surrey is not quoted in the foregoing, it may be mentioned as one of the counties in which the species is found. In Ireland Kane says that it is “abundant in certain localities in Munster; and in Co. Galway at Claring Bridge, and Oranmore; Cork; Killoghrum Wood, Enniscorthy; Blarney, Killarney.”
It is distributed throughout Central and Northern Europe, except the Polar region, and its range extends through Northern Asia to Amurland, Ussuri, and China.