This family of moths mainly comprises tropical species, and is but poorly represented in the Palæarctic Region. Only two species are European, and both occur in Britain.
As Cochlidion, Hübner, supersedes Limacodes, Latrielle, the name of the family so long known as Limacodidæ, will have to
be changed to that here adopted. Meyrick, who sinks Limacodes in favour of Apoda, Haworth, uses Heterogeneidæ as the family name.
The Festoon (Cochlidion (Heterogenea) limacodes).
The fore wings of the male are orange brown, more or less smudged or clouded with blackish; two oblique black lines, the first inclined inwards, and the second outwards and apparently terminating on the outer margin just above the inner angle, but there is a slender dusky curve from this point enclosing a clear, orange-brown spot. Hind wings blackish, except on the inner margin, which is broadly orange brown. Female, ochreous brown, with lines on the fore wings as in the male; hind wings suffused with dark grey or blackish, except on the inner area; generally rather larger than the male. (Plate [153], Figs. 1 ♂, 2 ♀.) Not infrequently, the fore wings of the male are so much clouded with blackish that the cross lines are obscured, and the spot on the inner margin alone remains clear.
The caterpillar (Plate [149], Fig. 1, from a coloured drawing by Mr. A. Sich) is green, with two reddish-edged yellow lines on the back; between these lines are yellowish spots; a yellow line along the sides extends along the front edge of the second ring, where it is marked with red. It feeds on oak, and may be beaten from the boughs in the autumn. The brownish cocoon is depicted on Plate [149]; Fig. 1a shows the hinged lid which covered the opening through which the chrysalis protruded previous to the moth's escape; Fig. 1b represents one from which the moth has not emerged, and in nature this would be attached to a leaf and covered with a delicate film of silk. The moth is out in June and July, and both sexes may be beaten from the branches of trees, or seen flying around their tops in the sunshine.
This species, often referred to as Limacodes testudo, and said to be the avellana of Linnæus, is an inhabitant of oak woods, and occurs in Hampshire, Sussex, Kent, Essex, Suffolk, Oxfordshire, Bucks, Gloucestershire, and Worcestershire. A male and two females have been reported from Clonbrock, Co. Galway, Ireland.
The Triangle (Heterogena asella).
The fore wings of this little species (Plate [153], Figs. 4 ♂ and 5 ♀) are of triangular shape; in the male, which sex is smaller than the female, they are dark brown, sometimes almost blackish (ab. nigra, Tutt), and those of the female yellowish brown varying to ochreous yellow (ab. flavescens, Tutt). The hind wings of the male are blackish, and of the female clouded with blackish.