[1] This species is endemic to New Zealand where it is found in the southwest districts of the South Island, including Westland, Otago Lakes and Fiordland.

Adults of I. petrograpta are on the wing from December to February and are attracted to sugar traps.

This species was described by Edward Meyrick in 1929 from a specimen collected by George Hudson near Lake Wakatipu in January.

Forewings elongate-triangular, termen obliquely rounded, waved; grey, irrorated blackish and whitish; a small white spot in middle of base; lines white, blackish-edged, waved, subbasal curved, first rather irregular, slightly bent on fold, second sinuate, subterminal parallel to termen, slightly indented near extremities; median band darker grey irrorated blackish, without white irroration, median shade obscurely blackish, dentate; spots outlined white and then blackish, claviform small, wedged-shaped, resting on first line, orbicular rather oblique, oval, reniform narrow slightly bent in middle : cilia grey narrowly barred white.

[5] This species is found only in the southwest portion of the South Island in the districts of Westland, Otago Lakes and Fiordland.

[2] This species inhabits tussock grasslands and shrublands in alpine and subalphine zones.