I. rubescens has a round or oval mark near the centre of the forewing that encloses a dot.

Larval hosts are likely herbaceous plants such as grasses and herbs and larvae have been reared on Gunnera prorepens.

This species was first described in 1879 by Arthur Gardiner Butler from a specimen obtained in Otago by Frederick Wollaston Hutton.

[3] Butler described the adults of this species as follows: Primaries sandy pale brown, with the ordinary markings (including the cuneiform external patch, and a diffused patch at external angle) ferruginous; reniform spot enclosing a blackish J -shaped marking, and bounded externally by two black dots; orbicular represented by a black dot, below which is an oblique ferruginous dash; a discal arched series of minute black dots on the veins; secondaries smoky-brown, with rosy-cupreous reflections, fringe and margin sandy -brown; body pale sandy-brown; thorax somewhat ferruginous down the centre; abdomen whitish at the base, with four brown-banded dorsal tufts; under surface uniform pale shining sandy-brown, with faint rosy reflections; discocellulars blackish.

Larval hosts are likely herbaceous plants such as grasses and larvae have been reared on Gunnera prorepens, a native ground cover species.