The colour of the larva is pale apple green, with a wide darker stripe down the back, two others along the sides, and two more between the latter and the dorsal stripe. All these five stripes are bordered with a whitish colour. The chrysalis is bright apple green, dotted with white, and the wing cases are striped with a purple-brown line edged with white. CHAPTER XV _THE HAIRSTREAKS, COPPERS AND BLUES_ 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 constitute 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 anal 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 butterfly 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. [Illustration: 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-album_)