We have one species.
ELVIA GLAUCATA, Walk.
(Elvia glaucata, Walk. 1431; Feld. cxxxii. 25. Elvia donovani, Feld. cxxxii. 5. Elvia glaucata, Meyr., Trans. N. Z. Inst. xvi. 65.)
(Plate [VI]., fig. 23 and 24 varieties.)
This very pretty insect is generally distributed throughout the country.
The expansion of the wings is about an inch.
The fore-wings vary from pale green to dark steely blue, rarely pale reddish-brown; there is an almost straight, black transverse line near the base; a broad curved line before the middle, shaded towards the termen; then a straight line, breaking up into dots towards the dorsum, followed by a conspicuous cream-coloured blotch near the costa; this again is followed by a fine jagged cream-coloured line; there is a terminal series of black dots. The hind-wings are cream-coloured, tinged with steely blue or green towards the termen; there are a few obscure transverse lines and a short series of dots from the dorsum. The apex of the fore-wing is very blunt, and the termen is slightly hollowed out towards the tornus; the termen of the hind-wings is deeply scalloped.
This species is extremely variable. In addition to the variations above indicated, the markings of many specimens differ considerably in intensity, and there are frequently several large cream-coloured blotches towards the base or middle of the forewings.
The perfect insect appears from September till March, but is not a common species. It frequents forest districts, and may sometimes be found at rest on tree-trunks, where the beautiful colouring of its fore-wings closely imitates that of certain lichens, and renders its detection in such situations extremely difficult. Unlike the insects included in the two preceding genera, this species closes its wings when at rest, the anterior pair alone being visible. These wings are not held flat, but are curiously folded longitudinally, and the end of the abdomen is also curled upwards. By slightly raising the insect above the level of the surrounding surface, this peculiar attitude considerably increases its resemblance to a lichen growing on the stem or branch of a tree. It will also be observed that in this species, which when at rest exposes only its fore-wings, these alone are protectively coloured; whilst in the genera Chloroclystis and Phrissogonus, where both pairs of wings are displayed, both pairs are protectively coloured.