IDAE--have only _four_ legs adapted for walking, whilst the _females_
have _six_.

* * * * *

THE BROWN HAIR-STREAK. (_Thecla Betulae._)

(Plate XII. fig. 1, Male; 1 _a_, Female.)

The genus to which this butterfly belongs, contains five British species,
elegant and interesting insects, though not gaily tinted. They are most
obviously distinguished from other small butterflies by the _tail-like_
projection on the lower edge of their hind wings (though one of their {141}
number, _T. Rubi_, has this very slightly developed). From each other they
are best distinguished by the characters on their under surface, where they
all bear a more or less distinct _hair_-like _streak_, whence their common
name--Hair-streak.

The Brown Hair-streak is the largest of the genus, measuring sometimes an
inch and two-thirds in expanse. The two sexes differ considerably on the
upper surface, the male being of a deep brown colour, slightly paler near
the middle of the front wing, while the female possesses on the front wing
a _large patch of clear orange_. Both sexes have several orange marks upon
the lower angles of the hind wings. Beneath, the general colour is tawny
orange with duller bands, and marked with one white line on the front wing,
and _two parallel white lines on the hind wings_.

The _caterpillar_ is green, marked obliquely with white; it feeds on the
birch and also on the sloe.

The _butterfly_ appears in August, continuing into September. It is
generally distributed through the south, but is by no means an abundant
insect. Mr. Stainton observes that it has a habit of "flitting along in
hedges just in advance of the collector;" but it is also found in oak woods
in company with the Purple Hair-streak.

Forty were taken in a season in woods near Henfield, Sussex. Other
localities are, Underbarrow Moss, Westmoreland; North Lancashire, common in
some parts; Preston; Valley of the Dovey, Montgomeryshire; {142} Cardiff,
S. W.; Barnwell Wold; Peterborough; Colchester; Epping; Darenth Wood;
Coombe Wood; Brighton; Tenterden; Winchester; Woolmer Forest, Hants;
Plymouth; Dartmoor; Wallingford, Berks; Ipswich; Dorsetshire; Norfolk;
Wiltshire; Monks Wood, Cambridgeshire.

* * * * *

THE BLACK HAIR-STREAK. (_Thecla Pruni._)

(Plate XII. fig. 2.)

The upper side is very dark brown, sometimes almost black, and bearing near
the _hinder_ edge of the _hind wings_ a _few o