(_Rhapsa scotosialis_, Walk., Suppl. 1150. _Herminia lilacina_, Butl., Proc. Zool. Soc. Lond. 1877, pl. xlii. 11. _Rhapsa scotosialis_, Meyr., Trans. N. Z. Inst. xix. 38.) (Plate VI., fig. 5 [M], 6 [F].) This remarkable species is extremely abundant and generally distributed throughout the country. The expansion of the wings is 1-3/8 inches. _The fore-wings have the costa considerably arched towards the apex, and the termen is bowed outwards in the middle_; the colour is pale brown in the male and dark brown in the female; there are several obscure black marks near the base; _the orbicular is very small, orange or pale grey outlined in black, the claviform is absent, the reniform is conspicuous, the outer edge is much indented, the inner edge is outlined with dull orange-red_, there is a black blotch between the orbicular and the reniform; beyond the reniform there is a curved transverse line enveloping a series of minute black dots, then a very conspicuous wavy transverse line shaded towards the base of the wing; _there is a pale triangular area at the apex_, and a series of small crescentic dark brown markings on the termen; the cilia are dark brown. The hind-wings are greyish-ochreous; there is a rather faint line across the middle, followed by a broad shade; a series of {37}small crescentic marks is situated on the termen; the cilia are dark greyish-ochreous. _The antennæ of the male are strongly bipectinated. The female is considerably darker, the markings are less distinct and numerous, and there is no black blotch between the orbicular and the reniform._ Some male specimens are much paler in colour than others, but with this exception there does not appear to be any important variation. The eggs are round, flattened above, bright green, becoming dull purplish about two days after being laid. The young larva when first emerged is about 1/8 inch in length; the head is brown; the body dull white, with a series of black tubercles round each segment, each tubercle emitting a tuft of bristles. The larva has sixteen legs, but the two anterior pairs of ventral claspers are not employed in walking, the caterpillar's mode of progression, consequently, resembling that of a larva with twelve legs only. The food-plant is _Piper excelsum_. The perfect insect appears from September till April, and is very common amongst undergrowth in the forest. It is seldom found in the daytime, but at night it is extremely abundant in densely wooded situations. It flies in a very stealthy manner, and may soon be recognised on the wing by this feature alone. When disturbed it always secretes itself amongst dead fern fronds or other vegetable refuse, where its sombre colour effectually conceals it. The costal fold on the under side of the fore-wing of the male contains a very large tuft of extremely long hairs. It probably emits a scent agreeable to the female. RHAPSA OCTIAS. Meyr.