The moth is out in June, sometimes late May; it is exceedingly local in Britain, and only occurs in the Breck district, where it was first met with about fifty years ago. Tuddenham, in Suffolk, is a noted locality, as also is Thetford, in Norfolk.
The Treble-bar (Anaitis plagiata).
This is a greyish white species, of which specimens of both generations are shown on Plate [55], Figs. 6 ♂, 7 ♀ (1st generation), Fig. 8 ♂ (2nd generation). The chief variation is in the cross central bars of the fore wings, which are sometimes much widened, and occasionally joined from the middle to the inner margin; or the space between these two bars is more or less filled up with dark grey. On the other hand, the bars are sometimes very faint, but such aberrations are perhaps most frequent in the second generation, which consists of smaller specimens.
The long caterpillar is brown, inclining to reddish or to greenish, with several darker and paler lines on the back and a yellowish line low down along the sides. It feeds on St. John's wort (Hypericum) in June and July; the caterpillars, hatching in the autumn, are not mature until the following April.
Usually there are two generations of the moth, the first appearing in May and June, and the second in August and September. The species is pretty generally distributed over the British Isles, extending to the Hebrides and the Orkneys; and will probably be found in all localities where its food plant occurs freely. It affects cliffs and sandhills by the sea, rough places on chalk slopes, and sometimes the moths fly up in numbers as we walk over the herbage in such spots.
The range abroad extends to Western India and Japan.
Manchester Treble-bar (Carsia paludata).
In general character this species somewhat resembles that last considered. It is, however, much smaller, and there are reddish clouds on the outer marginal area.