This pale ochreous species, an example of which is represented on Plate [21], Fig. 8, varies in the amount of darker shading or suffusion on the outer marginal area of the fore wing; sometimes this is grey-brown or pale reddish brown, but often there is no shading whatever, and in such specimens the ground colour is usually very pale. The dark brown reniform mark is always present, but the cross lines are more often absent than present.
The caterpillar is green, with a darker green line along the middle of the back, and a white stripe on each side of it, the inner edge of each of the latter irregular; head, greenish grey, and the bristle-bearing raised dots are shining green with a dusky cap. It feeds on Brachypodium sylvaticum, but seems to accommodate itself to a diet of Phalaris arundinacea, and would perhaps eat other grasses: August to May. (Plate [23], Fig. 3; after Hofmann.)
The moth is out all through the summer months, and
frequents marshes, damp rides and borders of woods, heaths, and where there is plenty of tall grass.
The species is widely distributed over England and Wales, although it appears to be rather scarce in the midlands and northwards. In Ireland it is generally abundant, but in Scotland it has only been noted from the south, and is there local and rare.
The distribution abroad includes Amurland, Corea, and Japan.
The Small Purple Barred (Prothymnia viridaria).
The fore wings of this species (Plate [21], Figs. 10 ♂, 11 ♀) range in colour from olive grey to olive brown, and are frequently adorned with two rosy-red (typical) or purplish bands (ænea, Haw.). In some specimens the bands are of a dusky hue and not very distinct, whilst in others the wings are of a uniform dingy brown tint (ab. fusca, Tutt).
The caterpillar (Plate [25], Fig. 2) is velvety-green above and paler beneath, yellowish between the rings, with a dark green slender line bordered by paler lines along the back, and three pale lines along the sides; below the yellowish spiracles there is a broader pale line becoming whitish on rings 9-12; head, green mottled with brown (adapted from Hellins).
It is to be found in August and September on the common milkwort (Polygala vulgaris). On May 31, 1906, I met with the moth in some numbers on a marshy bit of heath in Surrey, where there was a plentiful growth of lousewort (Pedicularis), but, so far as I know, no Polygala. All the moths were much below the average size, the bands were mainly purple, but in no case rosy. The moth flies in May and June, and specimens have been captured both earlier and later. Except that it does not appear to occur in the extreme north of Scotland, the species seems to be pretty generally distributed over the British Isles, and is often very common in many parts.