Ichneutica semivittata

This species was first described by Francis Walker in 1865 using a male specimen collected in Nelson by T. R. Oxley.[2] Walker originally named the species Leucania semivittata.[3] J. S. Dugdale discussed this species in his 1988 catalogue and placed it within the Tmetolophota genus.[4] In 2019 Robert Hoare undertook a major review of New Zealand Noctuidae.[2] During this review the genus Ichneutica was greatly expanded and the genus Tmetolophota was subsumed into that genus as a synonym.[2] As a result of this review, this species is now known as Ichneutica semivittata.[2]

Ichneutica semivittata illustrated by George Hudson

Living specimen of Ichneutica semivittata

George Hudson described the larvae of I. semivittata as follows:

The larva, which feeds on native grasses, is about 1+1⁄4 inches in length, subcylindrical, slightly tapering at each end; dull green, very finely streaked with reddish-brown; the dorsal and subdorsal lines are indicated by fine double reddish lines; there is a series of white dots, one on each segment, except on the second and last; the lateral line is very distinct, dark reddish-brown, shaded with cream colour below; the spiracles are blackish; the underside of the larva and the whole of the second segment is a paler and clearer green than the rest of the body.[5]

Walker described the adults of this species as follows:

Male, Very pale fawn-colour. Palpi hardly ascending, as long as the breadth of the head; second joint fringed beneath; third lanceolate, less than half the length of the second. Antennae setose. Abdomen extending somewhat beyond the hind wings. Wings with black marginal points. Fore wings acute, with a short black basal line ; the latter is accompanied by an ochraceous line which extends irregularly along the hind side of a brownish streak in the disk ; this streak is traversed by a curved line of black points ; veins towards the exterior border brownish, with brownish lines between them ; under side with a brownish patch in the disk beyond the middle. Hind wings brownish above, except along the interior border. Length of the body 9 lines ; of the wings 22 lines.[3]

The wingspan of the adult male of this species is between 30 and 42 mm and for the female is between 31 and 40 mm.[2] This species is distinctive and can be distinguished from other species as it has a reddish ochreous streak on the forewing.[2] The similar species I. sulcana can be distinguished from I. semivittata as the former is much larger, has a darker hindwing and abdomen and has only on to three spots located behind the middle of the forewing in comparison to the 8 or 9 of I. semivittata.[2]

It is endemic to New Zealand.[6] The species can be found from Three Kings Islands down to and including Stewart Island.[2]

This species lives in a variety of habitats from open grasslands to clearings in forest and at a range of altitudes from the sea level to the alpine zone.[2] It is relatively rare in the tussock grasslands of the MacKenzie country and in Canterbury.[2]

Adults of this species are on the wing from August to April and are attracted to light.[2]

Carex secta a larval host species of I. semivittata

Larval host species include Juncus procera, Carex secta as well as on tussock grasses such as Poa cita, P. colensoi and Festuca novae-zelandiae.[2]