Genus 3.—CHALASTRA, Walk.
"Face with a slight cone of scales. Palpi rather long, porrected, roughly scaled. Antennæ in male bi-pectinated. Fore-wings with vein 6 from below 9, 7 from below angle of areole, 10 very shortly touching 9, 11 free, 12 very shortly touching 11. Hind-wings normal."—(Meyrick.) (Plate [II]., figs. 51 and 52.)
This genus is represented by one species only.
I have made a very careful examination of several denuded specimens of Chalastra pelurgata, and I find that in the fore-wings veins 9, 10, and 11 rise almost from a point. Vein 10 afterwards approaches closely to 9, but does not actually touch it, and consequently does not form a true areole. Vein 12 also appears to me to be free.
CHALASTRA PELURGATA, Walk.
(Chalastra pelurgata, Walk. 1430. Itama cinerascens, Feld. cxxxi. 1. Stratocleis streptophora, Meyr., Trans. N. Z. Inst. xvi. 106.)
(Plate [IX]., figs. 33 and 34 ♂ varieties, 35 and 36 ♀ ditto; Plate [III]., fig. 21, larva.)
This species is very abundant in the neighbourhood of Wellington. It has also occurred at Palmerston North, and is probably common throughout the whole of the North Island. In the South Island it has been taken in the Otira Gorge, and at Dunedin, Otara and Invercargill.
The expansion of the wings is about 1⅜ inches. The fore-wings of the male vary from pale orange-brown to dull yellowish-brown; there is a doubly curved dark brown transverse line near the base; a broad straight line a little before the middle; a very strongly curved line a little beyond the middle, and a less strongly curved line near the termen, often composed of a series of triangular white dots edged with dark brown; all these lines are much stronger on the costa, and are sometimes almost obliterated elsewhere. The hind-wings are pale yellow, with several brown-edged white spots at the tornus, and an indistinct line parallel to the termen. The apex of the fore-wing is considerably produced, and there is a large rounded projection on the termen. The hind-wings have several small projections on the termen. In the female the fore-wings are pale yellow or orange, the transverse lines and white spots are usually more conspicuous, and the projections on the termen of the fore- and hind-wings larger.
This is a very variable insect, especially in the male, some specimens of which sex are very much clouded and dappled with dark brown both on the fore- and hind-wings. Many of these darker forms might readily be taken for distinct species, when compared with the pale orange-brown variety, but a good series of specimens presents numerous intermediate forms which completely connect these extreme varieties. The females also vary, but are never as dark as the males.