Summary

Richard South The Moths of the British Isles Second Series… (1909)

Wherever colonies of two of the kind exist within visiting distance of each other, there, it appears, we may reasonably expect to find hybrids.
From a number of cocoons collected in a Yorkshire locality for loniceræ, I reared, in 1907, a good many examples of that species, and also about a dozen six-spot specimens, which agree in colour with filipendulæ, but they have the vein-interrupted sixth spot and broad border to hind wings, as in hippocrepidis.
The caterpillar (Plate 145, Fig. 4) is greenish, with black markings and some yellow spots, the latter chiefly on the hind edges of the rings.
Source: Wikisource

Richard South The Moths of the British Isles Second Series… (1909)

Of the three species occurring in Britain this is slightly the larger, at least in the male. The fore wings are green, sometimes with a slightly golden sheen; fringes, greyish. The male is best distinguished from statices by its more slender body, and by the pectinated and rather pointed antennæ. The female is a good deal smaller than the male; the antennæ are simple, and somewhat thread-like, compared with those of the females of statices and geryon. (Plate 147, Figs. 6 ♂, 7 ♀.)
The caterpillar is green, with the raised spots inclining to bluish
Source: Wikisource

Richard South The Moths of the British Isles Second Series… (1909)

The chief differences are in the rather longer fore wings and the more pointed tips of the hind pair; the borders of the hind wings are often narrower. In a broad way, it may be stated that the general tone of colour in the male of loniceræ is bluer than that of trifolii. The union of any two or more spots is rarely seen in this species in Britain, but specimens with all the spots joined together have certainly been noted.
Source: Wikisource

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