About Ischalis nelsonaria (Felder & Rogenhofer, 1875)
This species has the scientific name Ischalis nelsonaria (Felder & Rogenhofer, 1875).
Hudson described the egg of this species as oval, flattened at one end, and pale sea green, covered in numerous very faint hexagonal depressions. Eggs are laid loosely in groups of two or three and are not anchored to a surface. In most specimens, a very large oval depression appears on each side of the egg’s long axis. As the egg develops, it turns yellowish and gains numerous irregular orange-brown markings.
When fully mature, the larva is approximately 35 millimeters (about 1 inch) long and brown in color. Hudson described the full-grown larva as elongate, slender, and cylindrical, with the head and thoracic segments slightly flattened. Its dorsal general color is a dull greyish brown, with fine transverse stripes of lighter and darker shades. Its ventral side is dull pinkish-brown, also dotted and striped with lighter and darker tones. The top of the head is blackish-brown. A distinct white-edged dorsal band runs from the antennae to segment 5, and a darker ventral stripe is present in the thoracic region. Two distinct black spots appear on the back of segment 5, as well as on the sides of segments 9 and 10 and at the base of the ventral proleg. Segments 11, 12 and 13 are very short, while the other abdominal segments are elongate. A distinct pinkish-white lateral ridge runs along segments 5 through 10 inclusive. The larva has numerous small warts and very short bristles.
Hudson also described the adult of the species. Male wingspan is 1+1⁄4 inches, while female wingspan is 1+5⁄8 inches. Male forewings are rich reddish-brown, mottled with darker shades. Several small white marks sit on the costa, there is a black discal dot, and an almost straight white transverse line beyond the three-quarter point of the wing. Outside this line, the wing is speckled with greyish-white. Male hindwings are pale pinkish-brown or purplish-brown, with a black discal dot and a curved wavy blackish transverse line just beyond the middle of the wing that continues the transverse line from the forewing. Beyond this line and on the dorsum, there are usually several small blackish markings.
Female forewings are orange-red, speckled with darker shades. A doubly curved wavy transverse line sits at about 1⁄3 of the wing length, and an almost straight transverse line sits beyond 3⁄4, both dark red. Female hindwings are pale reddish-orange, often tinged with purple, with a curved wavy blackish transverse line. In both sexes, the forewing apex is projecting, and a strong rounded projection sits on the termen just above the middle; the hindwing termen also has several small projections. Adult males are very variable in color, while adult females are also variable but less so than males. Weintraub and Scoble noted that the genitalia of this species are distinctly different from those of other species in the Ischalis genus.
Ischalis nelsonaria is endemic to New Zealand. It has been observed in both the North and South Islands and is considered widespread, though it is less common than other species in the genus Ischalis. This species lives in native forest. Its known larval host is Zealandia pustulata, and larvae have also been reared on the fern Blechnum novae-zelandiae. Adults have been observed feeding on flowers of Metrosideros diffusa.
