Family--LYCaeNIDae
This is a large family, including as it does no less than nineteen of the British species. These are all of small size, and are characterised by their short and jerky flights. They seldom rise much above the ground, and are consequently very easily caught.
The caterpillars of this family have all short and rather thick bodies, shaped very much like that of the wood louse--flattened beneath and very convex above.
The chrysalides are generally attached by the "tail," and further secured by a silken cord round the body, as we have already observed in the case of the _Pieridae_.
The perfect insects differ from the preceding species in that all six legs are perfectly developed and adapted for walking.
There are only three genera in this large family:
1. _Thecla_--The Hairstreaks, with "tailed" wings.
2. _Polyommatus_--The "Coppers."
3. _Lycaena_--The "Blues," with wings either blue or brown.
_The Brown Hairstreak_ (_Thecla Betulae_)
The five Hairstreaks which const.i.tute the genus _Thecla_ are all pretty insects, characterised by hair-like streaks on the under surface.
_Betulae_ is the largest of these. Its upper surface is of a deep brown colour, with orange-brown marks at the a.n.a.l angles of the hind wings, and, in the female, a large patch of orange on the fore wings. The under side (Plate VI, fig. 3) is orange brown, much lighter in the male than in the female. On the fore wings are two white lines, the inner one of which is indistinct; and on the hind wings are two others, the outer one being longer and more distinct than the inner.
This b.u.t.terfly is by no means an abundant insect, though it is widely distributed, and in some places plentiful. Its chief haunts are woods, and we may mention among its favoured localities Epping Forest, Monk"s Wood in Cambridgeshire, the wooded parts of South Devon and Dorset, New Forest, Colchester, and Peterborough.
[Ill.u.s.tration: FIG. 83.--THE BROWN HAIRSTREAK--MALE.]
The perfect insect is on the wing from July to October, and the eggs are deposited in the autumn on the twigs of its food plant--the blackthorn (_Prunus spinosa_). These do not hatch till the following spring. Toward the end of June the caterpillar is fully fed.
The colour of the caterpillar is light green, with two white stripes down the back, and two others along the sides. There are also two small oblique whitish lines on each side of each segment.
The chrysalis is smooth, and of a pale brown colour.
_The Black Hairstreak, or White-letter Hairstreak_ (_Thecla W-alb.u.m_)
The first of the above two popular names has been applied to this species on account of the very deep brown colour of the upper side, which colour is often a near approach to black. The second is due to the W-shaped bend of the white streak of the hind wings. The ground colour of the under side (Plate VI, fig. 4) is greyish brown, with a bright orange band, spotted with black near the hind margin of the hind wings.
[Ill.u.s.tration: FIG. 84.--THE WHITE-LETTER HAIRSTREAK.]
_W-alb.u.m_ is a somewhat rare insect, but is occasionally seen in plenty in a few localities, Cambridgeshire, Berkshire, Epping, Colchester and Suffolk being among its chief resorts. It is out on the wing in July, and should be looked for in wooded country where the common elm (_Ulmus campestris_) and the wych elm (_U. montana_), its food plants, exist.
The eggs are laid on the twigs of these trees late in the summer, and the young caterpillars do not appear till the following spring. The chrysalis may be found attached to an elm twig or leaf about the end of June.
The caterpillar is pale green. The ridges along the back are tinged with yellow, and there are two fine oblique white lines on each side of each segment.
_The Dark Hairstreak_ (_Thecla Pruni_)
The upper side of this b.u.t.terfly is very much like that of _W-alb.u.m_, but it may be distinguished by the presence of a few orange spots near the a.n.a.l angle of the hind wings. The colouring of the under side (Plate VI, fig. 5) is also very similar, except that the white lines of the wings are thinner and less distinct than in the last species, and do not exhibit the W-shaped bend. The orange band of this surface is bordered on each side with a row of black spots, each of which is touched with a bluish white or a metallic blue.
This insect is not by any means common, but has been seen in considerable numbers in certain localities. It is not found in either Scotland or Ireland, and its chief haunts in England seem to be in Huntingdonshire, Cambridgeshire and Northamptonshire. It frequents wooded country, and flies during June and July.
The eggs are laid late in the summer on the twigs of the blackthorn (_Prunus spinosa_), and are not hatched till the following spring.
The caterpillar, which is pale green, with rows of yellow spots, may be found in May.
_The Purple Hairstreak_ (_Thecla Quercus_)
This pretty b.u.t.terfly, by far the commonest of the Hairstreaks, though comparatively very small, reminds one forcibly of the n.o.ble 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 s.e.x.
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 a.n.a.l 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.
[Ill.u.s.tration: FIG. 85.--THE PURPLE HAIRSTREAK--MALE.]
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 larvae 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 b.u.t.terflies 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.
[Ill.u.s.tration: FIG. 86.--THE GREEN HAIRSTREAK.]
The upper side is dark brown, displaying metallic reflections when viewed in a strong light. The under side is represented in fig. 7 of Plate VI.
The chief food plants of this species are the bramble (_Rubus fruticosus_), the birch (_Betula alba_), and the broom (_Cytisus scoparius_).
The perfect insect flies in May and June, and the eggs are deposited during the latter month on the above plants. The caterpillars are full fed in July, and change to the chrysalis state towards the end of the summer.
The colour of the caterpillar is pale green, with a yellow stripe and several white oblique lines along the sides, also a yellowish stripe down the back.
The chrysalis is short and thick, and of a dark brown colour.
_The Large Copper_ (_Polyommatus Dispar_)
Our next genus contains only two British species. The first of these--the Large Copper--was once a common insect at Whittlesea in Cambridgeshire, and in some of the fens of Huntingdonshire, but is now feared to be quite extinct, as none have been seen for many years. The last capture was made in 1847 in Huntingdonshire. However, it _may_ turn up again; and even if it does not, it would be a pity to allow the memory of so fine an insect to die out; so we find room to figure it (Plate VI, fig. 8), and append a few remarks.
There is a very great difference between the male and the female. The former is of a brilliant copper hue, and all the wings have a black margin and a black streak near the middle. The female is larger; and the coppery colour is much redder. The black border of the fore wings is wider, and there are also several large black spots on these wings. The hind wings are almost entirely covered with black, with the exception of a broad coppery band near the hind margin.
The food plant of the caterpillar appears to have been the water dock (_Rumex Hydrolapathum_), on which the eggs were laid late in the summer.