By some systematists this small group of moths is treated as a subfamily of
the Geometridae. _Brephos_, however, which is typical of the family, does
not seem to have any close affinities with the Noctuidae or with the
Geometers, and is therefore better considered as apart from both those
families. Meyrick includes _Brephos_ with _Aplasta_, _Erannis_, and
_Baptria_, in his family Monocteniadae.
Only five species are known to inhabit the Palaearctic Region, and two of
these occur in Britain.
THE ORANGE UNDERWING (_Brephos parthenias_).
The white markings of the fore wings vary a good deal in size; in some
specimens, chiefly males, they are very small and confined to the front
margin; in others, mainly females, they are much enlarged, and the central
one is continued as a band across the wings. On the orange hind wings the
blackish {98} central band is usually more or less complete, but sometimes
it is nearly or quite absent above the blackish triangular patch on the
inner margin. Occasionally, there is a yellow blotch at the anal angle, and
frequently another on the costal area. Still more rarely the whole ground
colour is yellow. (Figured on Plate 38, Figs. 1 [male] and 2 [female].) The
caterpillar is green, with six white lines along the back, and white
stripes along the sides. When young it feeds on the catkins of birch, and
afterwards on the foliage. April to early June. (Plate 39, Fig. 1.)
The moth is out in March and April, and on sunny days the males may be seen
flying, generally pretty high up, on the lee side of the birch trees
growing on heaths; also in open spaces in or around birch woods. The
females rest on the twigs, as also do the males when the sun is obscured.
Both sexes have been found sitting on the ground in sunny glades.
The species is widely distributed over the southern and eastern counties,
common in many parts; but its range extends through England to Durham, and
it has been recorded from Wales. Although it does not seem to have been
noted in Scotland south of Kincardineshire, it occurs on the east to Moray.
Westmeath is the only Irish locality that has so far been mentioned.
Its distribution abroad extends to East Siberia and Amurland.
THE LIGHT ORANGE UNDERWING (_Brephos notha_).
Very similar to the last species, but rather smaller in size, and the fore
wings are much less variegated. The antennae of the male of this species
are bipectinated, whilst those of _parthenias_ are finely serrated. (Plate
38, Figs. 4 [male] and 5 [female].)
[Illustration]
2 Pl. 38.
1, 2. ORANGE UNDERWING.
3. THE REST HARROW.
4, 5. LIGHT ORANGE UNDERWING.
6-8. GRASS EMERALD.
[Illustration]
2 Pl. 39.
1. ORANGE UNDERWING: _caterpillar_.
2, 2a. LIGHT ORANGE UNDERWING: _caterpillar and chrysalis_.
3. LESSER BELLE: _caterpillar_.
{99} The caterpillar feeds in May and June on aspen, eating the foliage and
hiding between two leaves drawn together. The head is greenish or
greenish-brown, with three conspicuous black spots. Body, green,
olive-green, or reddish; line along middle of the back darker green edged
with white; two thin white lines on each side, and a whitish stripe along
the spiracles. When mature it burrows into decayed bark or wood (virgin
cork in confinement), and before changing to a reddish-brown chrysalis, it
spins a thin covering of silk and woody particles over the mouth of the
chamber. The caterpillar and the chrysalis are shown on Plate 39, Figs. 2
and 2a. Although the bulk of the moths emerge the following April, some
have been known to remain until the following or even the third year. The
males fly about aspen, but only in the sunshine; in other respects its
habits are pretty much those of the last species.
The distribution of the species in England seems confined to two areas: a
western one represented by Worcester, Gloucester, with Monmouth, Wales,
Wilts, and Dorset; and an eastern one by Norfolk, Cambridgeshire, Suffolk,
Essex, Middlesex, Kent, Surrey, and Sussex. In Scotland only recorded from
Moray.
The range abroad extends to Amurland.