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]
The _Notodontina_ are characterized as follows:--
"The maxillary palpi are obsolete. Fore-wings with vein 1b usually furcate, but with lower fork often weak or tending to be obsolete, 5 rising not nearer to 4 than to 6, parallel, 7 and 8 out of 9. Hind-wings almost always with frenulum, 1c absent. (Plate II., figs. 19 to 64, and Plate I., figs. 12 and 13.)
"Imago with fore-wings more or less broad-triangular; hind-wings broad-ovate."--(Meyrick.)
Larva (in New Zealand) generally with 10 or 12 legs only (Plate III., figs. 12, 17, 18, 19, 20, 21, 22, and 24), rarely with 16 (_Sphinx_, Pl. III., figs. 13 and 14).
"Pupa with segments 9 to 11 free; not protruded from cocoon in emergence."--(Meyrick.)
This is a very extensive group of the Lepidoptera, and so far as it is represented in New Zealand is equivalent to that group formerly known as the _Geometrina_, with the addition of the family _Sphingidæ_. The insects here included comprise many of our most interesting, abundant, and beautiful species. Some of them are so extremely variable that it is often a matter of considerable difficulty to determine the most convenient points on which to base the specific distinctions; although fortunately great advances have been made in this direction of late years owing to the increase in the number of workers, and the consequent accumulation of available material. In connection with this portion of the subject, special mention should be made of Mr. Meyrick's paper on the group, which appeared in the 'Transactions' of the New Zealand Institute for 1883. This essay has been of the greatest value in dispelling the doubts which formerly existed respecting the limits of many of the most variable species.