Dark Underwing Wainscot

Eggs of this species are hemispherical in shape and green in colour with a honeycomb on the surface.

George Hudson described the larva of this species as follows:

The full grown larva is about 1+3⁄4 inch in length, much attenuated posteriorly, pale reddish-ochreous, with numerous fine wavy darker lines; the subdorsal and lateral lines are straight and much more conspicuous; the spiracles are black, and there is a dark olive-green line down the midback.

George Hudson described the adults of I. sulcana as follows:

The expansion of the wings is from 1 1/2 to 1 3/4 inches. The fore-wings are light ochreous with the veins white; there is a shaded, brownish, longitudinal streak near the apex, another from the end of the cell to the termen, a stronger streak from the base of the wing to near the tornus, and another along the dorsum; there is a minute black dot near the base above the middle, a slightly larger dot at about one-third, a conspicuous dot between the origins of veins 3 and 4, and a very minute dot on vein 6. Hind-wings dark blackish-grey, cilia paler. The wingspan of the adult male of this species is between 35 and 46 mm and for the female is between 42 and 48 mm. Specimens from the northern North Island can be smaller and have more pronounced shading on the forewing. I. sulcana and I. …

This species is endemic to New Zealand. I. sulcana are fairly common and are found throughout the North, South and Stewart Islands at a range of altitudes from the lowlands to the alpine zone. This species is said to be more common in the North Island.

Adults of this species are on the wing from December to May but have been recorded as on the wing in August and September in the northern parts of the North Island. Adults are attracted to light and have been collected via sugar traps as well as a mercury vapour light trap.