Netted Mountain Moth (Fidonia carbonaria).
The white wings of this species (Plate [141], Figs. 1 ♂, 2 ♀) are freckled with blackish and crossed by black stripes; sometimes the freckling is so heavy that the white ground colour is much obscured and only distinctly seen as edging to the cross stripes.
The caterpillar is dingy ochreous or whity brown marked with wavy darker stripes. It feeds at night on birch and sallow; Vaccinium, Erica, bearberry (Arctostaphylos uva-ursi) have also been mentioned as food plants.
In April and May, the moth, which is to be found locally, high up on the mountains of Scotland from Perthshire to Ross, is on the wing, and flies in the sunshine. Writing of this species at Rannoch in May (about 17th), 1905, Mr. E. A. Cockayne remarks that the moths began to fly about noon,
when they appeared on all sides and were fairly active on the wing.
The distribution abroad is northern and Alpine, and the range extends to North-east Siberia.
Frosted Yellow (Fidonia limbaria).
This black-bordered orange-yellow species (Plate [141], Fig. 3) is not likely to be confused with any other occurring in Britain. The wings are more or less sprinkled with black, but this is usually most noticeable on the hind wings which are sometimes thickly sprinkled, or, more rarely, the yellow ground colour is entirely obscured. The form with a black discal spot on all the wings has been named ab. quadripunctaria, Fuchs. In ab. fumata, Mathew, the orange yellow is replaced by smoky umber brown, tinged with orange, and dusted with black atoms (bred July, 1899).
The caterpillar is greenish with grey-edged yellowish lines along the back, and a black-edged yellow one along the sides. The ground colour is sometimes purplish brown. It feeds on broom chiefly, but will eat other Genisteæ. There appears to be two broods, one in June, and the other in September, or earlier sometimes. The moth is out in May and early June, and again in July and August, but it has been known to remain in the chrysalis for four years. It flies in the sunshine, and when resting, it sits like a butterfly, with its wings brought together over its back.
Stephens (1831) states that the species was "not uncommon among high broom in the vicinity of Birch-wood in Kent." Later authors give Stowmarket (common), Needham, Barham, and Ipswich, in Suffolk. There are no recent records from the county of Kent; and not much has been heard of the species from Suffolk, although it may still exist, in greatly reduced numbers, in some of its old haunts therein.