Ichneutica epiastra

This moth was first described by Edward Meyrick in 1911 and named Leucania epiastra.[3] The male lectotype specimen is held at the Natural History Museum, London.[4] In 1988 J. S. Dugdale, in his catalogue on New Zealand lepidopera, placed this species within the Dipaustica genus.[4] In 2019 Robert Hoare undertook a major review of New Zealand Noctuidae species.[2] During this review the genus Ichneutica was greatly expanded and the genus Dipaustica was subsumed into that genus as a synonym.[2] As a result of this review, this species is now known as Ichneutica epiastra.[2]

George Hudson described the eggs of I. epiastra as follows:

The egg is spherical, flattened at the base, and rather coarsely ribbed, the ribs radiating from the micorpyle. The colour is at first a uniform pale yellow but after a few days the micropyle becomes dark brown and a dark brown circle appears round it.[5]

Hudson went on to describe the larva of this species:

Illustration of I. epiastra larva by Hudson

The full grown larva is 1+7⁄8 inch in length, dull brownish green in colour, sometimes tinged with reddish brown, especially on posterior segments. The dorsal and subdorsal lines are very narrow but fairly well marked; dull white in colour faintly edged with red or reddish brown. The lateral line is somewhat indistinct, white in colour. On it are situated the spiracles which are dull cream-colour edged in black. The lateral line is often edged with small brown blotches situated above the spiracles, and on the anterior segments these blotches are sometimes joined to form a broad, faintly marked upward edging to the lateral line. The integument, especially on the dorsal surface, has a number of fine white branching veins, and on each segment is a number of minute black dots from which spring short brown bristles. The prolegs are of the same colour as the body, edged with dark-brown hooks. The head is horny, amber in colour, mottled and netted with brown. [5]

Hudson goes on to state that the pupa appears light brown in colour initially and then turns a shiny very dark brown.[5]

Meyrick first described the adults of this species as follows:

♂♀. 40-44 mm. Head and thorax light greyish-ochreous, thorax with two pairs of fine oblique black lines or series of specks, prothorax with strong triangular crest. Antennae in ♂ moderately fasciculate-ciliated. Abdomen pale greyish-ochreous with fine black specks, densely hairy towards base. Anterior tarsi with two apical joints black. Forewings light - brownish, with scattered black specks, towards base and costa suffused with light greyish-ochreous ; first line represented by two or three black dots, second line by a series on veins ; two white dots longitudinally placed about lower angle of cell, connected by grey suffusion ; a terminal series of black dots between veins : cilia light brownish-ochreous. Hindwings fuscous, paler and tinged with pale greyish-ochreous towards base ; cilia whitish-ochreous, tips whitish.[3]

Hudson also described the adults of this species:

Watercolour illustration by Hudson of adult I. epiastra

The expansion of the wings is 1+5⁄8 inches. The forewings are pale brown with a broad, cloudy longitudinal streak, containing two white dots near the middle of the wing; there are numerous minute black specks, especially on the central area; two black dots indicate the position of the first line and a curved row of similar dots marks the second line; there is also a series of terminal dot. The hindwings are dark, brownish-grey, with pale brown cilia tipped with white.[5]

Live specimen of I. epiastra

This species is variable in both colour and size.[2] The colour of adults of this species can range from pale to pink ochreous up to a deep brown.[2] The adult male wingspan is between 33 and 43 mm and the female wingspan is between 38 and 45 mm.[2] There are specimens that have been collected at Ōkārito in Westland that are regarded as a dwarf form of I. epiastra as they are very similar both in appearance and in genitalia but are smaller than the typical I. epiastra.[2] The dwarf Westland form male has a wingspan of between 32 and 33 mm and the female has a wingspan of 32 mm.[2] I. epiastra can be confused with the similar species I. arotis and I. haedifrontella.[2] I. epiastra has small projections on its head that are diagnostic though these are sometimes difficult to discern.[2] In comparison to the other two species these tubercles are long and sharp tipped.[2] A row of black dots can be seen on the forewing of I. epiastra where as I. arotis, has faint dashes, if any markings at all, on a similar part of its forewings.[2] I. haedifrontella only has short and blunt tubercles on its head.[2] This is the only visible feature that distinguishes I. haedifrontella from I. epiatra although male I. haedifrontella have distinctive genitalia that can be seen via dissection.[2]

I. epiastra is endemic to New Zealand.[6] This species is found throughout the North, South and Stewart Islands.[2]

This species lives in open habitats such as wetlands, dunes and forest clearings.[2]

Eggs of this species are laid in summer or autumn and larvae feed during winter and spring.[5] The larvae feed at night.[5] During the day larvae hide in the bases of the leaves of their host species.[5] When ready to pupate the larva journeys to the flower stem of its host, eats into the internal part of the stem and makes a chamber at the joint.[5] This is where the larva spends several weeks before pupating.[5] In preparation, just prior to pupating the larva will create a hole at the top of the chamber leaving only a thin layer of plant material to cover the hole.[5] After approximately six weeks the adult moth emerges - normally in the evening between 7pm and 9pm.[5] Adults are on the wing between October and February.[2] This species appears reluctantly attracted to light.[2] It does however come more frequently to the brighter mercury vapour traps.[2]

Austroderia toetoe, a host plant for I. epiastra larvae

The plant host species for the larvae of I. epiastra are in the genus Austroderia.[2]