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. Genus 6.--HYDRIOMENA, Hb. "Face with somewhat projecting or loose scales, or with conical tuft. Palpi rough-scaled. Antennæ in male ciliated, rarely dentate or naked. Abdomen not crested, or with crests on two basal segments only. Fore-wings with areole double. Hind-wings with 8 anastomosing with cell from near base to beyond middle. (See Plate II., fig. 32 head, figs. 33 and 34 neuration of _Hydriomena deltoidata_.) "A very large genus, principally characteristic of temperate regions in both hemispheres.--(Meyrick.) There are twelve New Zealand species. {47}HYDRIOMENA GOBIATA, Feld. (_Cidaria gobiata_, Feld. cxxxi. 2. _Phibalapteryx simulans_, Butl., Cist. Ent. ii. 506. _Phibalapteryx undulifera_, Butl., Cist. Ent. ii. 506. _Phibalapteryx anguligera_, Butl., Cist. Ent. ii. 507. _Phibalapteryx rivularis_, Butl., Cist. Ent. ii. 507. _Scotosia gobiata_, Meyr., Trans. N. Z. Inst. xvi. 70. _Cephalissa gobiata_, ib. xviii. 184.) (Plate VI., fig. 43 [M], 44 [F].) This insect has occurred plentifully at Wanganui and Wellington in the North Island, and is generally distributed throughout the South Island.