(Photo by W. J. Lucas.)
By some authorities the double-brooded bistortata is
considered specifically distinct from the, normally, single-brooded crepuscularia; others hold the opposite view. The March and April moths are generally rather browner in colour than those appearing in May and June, but I have some specimens taken in Wiltshire at the end of March, which are quite as pale as any example in the May-June series. Probably, we should be right in regarding crepuscularia as the older stock from which the double-brooded race, bistortata, has sprung. The former has a more extensive range, as it inhabits Northern Europe (Sutherlandshire in British Isles), whilst bistortata seems to be confined to Central Europe. A Perthshire form of the May-June race is shown on Plate [136], Fig. 7; and an example of ab. delamerensis, White, from Delamere Forest, Cheshire, is represented by Fig. 8. Figs. 6 ♂, 7 ♀, represent examples of the March and April race. Black or blackish forms, with the sub-marginal line more or less distinctly white, occur in both races, chiefly in Glamorganshire, South Wales.
A photograph, by Mr. H. Main, of the caterpillar, is reproduced on Plate [138], Fig. 3. The general colour is grey, inclining to yellowish or brownish; sometimes it is reddish brown; two broken dark-grey lines on the back, and some pale blotches on the sides. The caterpillars of the first race (bistortata) feed in May and June, and again in August and September. Those of the second race in June and July, or later. They seem to eat the foliage of trees, including those in orchards.
Note.—Cross-pairings between bistortata ♂ and crepuscularia ♀ resulted in the ab. ridingi, Tutt, whilst the offspring of a crossing of crepuscularia ♂ and bistortata ♀ have been named bacoti, Tutt. Pairings of bistortata ♂ and delamerensis ♀ produce ab. ridingi-suffusa, Tutt; and those of delamerensis ♂ and bistortata ♀ = bacoti-suffusa, Tutt. Further, bacoti-suffusa will pair with ridingi-suffusa, or the last named with crepuscularia; the progeny being in the first case mixta, Tutt, and in the latter, reversa, Tutt.
Brindled White-spot (Tephrosia luridata).
Two examples of this species (also known as extersaria, Hübner) are depicted on Plate [137], Figs. 1 ♂, 2 ♀. There is variation in the amount of black speckling and in the strength of the cross lines.
The caterpillar is dull hazel or chocolate brown, often tinged with green; a row of whitish dots on each side of a series of pale spots along the middle of the back; rings 4 and 8 barred with black-brown or dusky rust colour. Sometimes the general colour is green. (Adapted from Fenn.) It feeds in July and August, or even later, on oak and birch, sometimes on alder and sallow. The moth is out in May and June, earlier or later in some seasons. In Britain apparently confined to England, where it occurs locally, in woods, from Worcestershire
southwards to Kent and Cornwall, and eastward to Norfolk and Suffolk. In the New Forest, Hampshire, where it is often plentiful, it may be seen on the boles of trees, but is more easily obtained after dark when it comes to the sugar patch.