The young larva when first emerged is about ⅛ 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.
(Hyperaucha octias, Meyr., Trans. Ent. Soc. Lond., 1897, 383.)
(Plate [VI]., fig. 7.)
This interesting little species has recently occurred in some numbers in the neighbourhood of Wellington. I have no record at present of its capture in any other New Zealand locality.
The expansion of the wings is about 1 inch. The fore-wings have the costa straight, and the termen with a large projection slightly above the middle; the colour is pale brown; there is a broad dark brown patch on the costa at the base, a jagged transverse line at about one-fourth, a very broad, oblique, blackish-brown, oblong patch on the costa at about one-third; beyond this patch is situated the reniform which is very large, indented towards the termen where it is outlined in dark brown; there is a very fine jagged transverse line from beneath the reniform to the dorsum; a large irregular patch of dark brownish-black just before the apex, and an obscure transverse line; there is a series of minute, dark brown, crescentic marks on the termen. The hind-wings are dull whitish-grey; there is a faint blackish dot in the middle, a wavy line a little below the middle, and a terminal series of small dark marks. The antennæ are filiform in both sexes.
The perfect insect appears in October, November and December. It frequents dense forest ravines, and is generally disturbed from amongst dead leaves or old fern fronds. It is usually a very scarce species, but appears to be much commoner in some years than in others. According to Mr. Meyrick, it is also found in Australia.
This species is placed by Mr. Meyrick in the genus Rhapsa. The simple antennæ and absence of the broad costal fold in the males would appear, however, to remove it from that genus, as restricted by him in the 'Transactions' of the New Zealand Institute, xix. 38. In all other respects it appears to conform to the genus.[[25]]