Helastia semisignata

It was first described by Francis Walker in 1862 using specimens collected by A. Sinclair in Auckland and originally named Larentia semisignata.[4][3][2] In 1877 Arthur Gardiner Butler synonymised Cidaria dissociate and Cidaria semisilata with L. semisignata.[5] In the same publication Butler also mistakenly synonymised Larentia corcularia with L. semisignata.[5] This taxonomic error was correct by R. C. Craw in 1987.[2] In 1912 L. B. Prout placed this species in the genus Xanthorhoe.[6] This placement was followed by George Hudson in his 1928 book The butterflies and moths of New Zealand.[7] Subsequently, in 1971, J. S. Dugdale placed this species in the genus Helastia.[8] R. C. Craw confirmed this placement in his revision of the genus in 1987.[2] The male holotype is held at the Natural History Museum, London.[3]

H. semisignata male

Walker described this species as follows:

Cinereous, minutely black-speckled. Head wanting. Fore wings with several denticulated blackish lines, some of which are most conspicuous on the veins, where they form black points; middle space without lines, containing the black transverse elongated discal point; interior, exterior and submarginal lines formed by whitish points on the veins; marginal lunules black; costa convex; exterior border hardly convex. Hind wings paler, with indistinct lines. Length of the body 4 lines; of the wings 12 lines.[4]

Species in the genus Helastia can be difficult to distinguish from one another.[9] However this species normally has orange scaling present on its forewings and its wing veins have black and white patches.[9]

This species is endemic to New Zealand.[1] It is found in the North Island only.[9]

H. semisignata can be found in a variety of habitats at a variety of altitudes including native forest and scrubland, subalpine herbfields and in coastal areas.[9] This species also inhabits developed areas such as parks and gardens.[9]

Adults are on the wing from most frequently from October until March and are attracted to light.[9][10] They are nocturnal with adults resting on trees or stones during the day.[9]

H. semisignata larva.

Larvae of this species have been raised on mosses.[9] But other sources state that larvae have been reared on Pimelea foliage or that they feed on herbs.[11][12] These inconsistencies have resulted in Robert Hoare stating that further investigations into the life history of this species is needed.[9] The adult moths have been observed visiting and likely feeding from the flowers of Hoheria lyallii, Olearia virgata andVeronica salicifolia.[13][14]