This species was known to Haworth, but, as a British insect, was exceedingly rare until 1859, when Dr. Knaggs found some caterpillars upon poplar in the neighbourhood of Folkestone. From the stock then obtained the moths were reared in numbers for some time. Batches of eggs were also put down in various localities, and the species seems to have flourished in some of them for a while, but failed eventually to establish itself in any of them. Then the species disappeared from the Folkestone locality, although a caterpillar or two were found there in 1861, and on to 1912 in other places on the Kentish coast. In 1893 eggs were obtained at St. Leonard's, in Sussex, and thus originated a new stock.
The species has a wide range in Central and Northern Europe, extending to some of the southern parts; it also occurs in Siberia, Amurland, China, and Japan.
The Small Chocolate-tip (Pygæra pigra).
This species will be recognized by its smaller size and less distinct chocolate blotch on the tips of the fore wings. The ground colour varies from whitish grey to pale brownish grey; the pale cross lines are usually well defined; the first is bordered with chocolate colour, and angled above the middle; the third line runs from a white spot on the costa and through the chocolate patch. The moth is shown on Plate [35], and the early stages on Plate [34].
Of the offspring resulting from eggs laid by a female curtula that had paired with a male pigra, and also those from a female pigra crossed with a male curtula, the hybrids in each case most nearly resembled the female parent.
The eggs are pale olive green tending to brownish, and all that I have seen have been laid in irregular lines on leaves, or
on the sides of a chip box. The caterpillar is greyish, with some short hairs and black dots; the back is broadly marked with yellow, and there is a yellow stripe, with black dots on it, low down on the sides; rings four and eleven have each a raised black spot; head blackish. Feeds from June to September, on dwarf sallow (Salix repens), and also on young plants of aspen. Like other caterpillars of this genus, it hides by day in a packet of leaves spun together. There are certainly two broods, if not more, in the year. The moth emerges in May, and more irregularly in July or August, and October. Except when attracted to a light, the moth is rarely seen, but in fens, marshes, and boggy places generally, the caterpillars may often be obtained in numbers almost throughout the United Kingdom. Its distribution abroad embraces Northern and Central Europe, with extension into Northern Spain and Italy; Bulgaria, South-east Russia, and Armenia.
THYATIRIDÆ.
The nine British species next to be considered belong to the old family Cymatophoridæ, but as the name Cymatophora, as indicated by Hübner in the "Tentamen" (1816), is now generically used by authors for some species of Geometridæ; and as Hübner's Verzeichniss generic names will have to be used for the species previously included in Cymatophora, Tr., the term Thyatiridæ has here been adopted for this family—the Polyplocidæ of Meyrick and others.