Larval hosts include species in the genera Cortaderia and Schoenus as well as Phormium tenax.

I. blenheimensis can be distinguished as even when worn and pale it has blackish forewing fringes that I. arotis lack.

I. theobroma might possibly be confused with the "northern dark" form of I. arotis but can be distinguished as I. theobroma has broader wings and doesn't have the pale markings on the forewing that the "northern dark" form of I. arotis has.

I. epiastra can be distinguished as it has an obvious row of black dots along the outer margin of the wing where as I. arotis is either lacks these marks or has brown dashes.

This species was first described by Edward Meyrick in 1887 from specimens collected in Blenheim, Christchurch and Rakaia in November and December.

General colour dull reddish-ochreous, with numerous darker, slightly wavy, longitudinal lines.

A double, slender brownish-red dorsal line, with pale interspace, very conspicuous; a similar, but slightly fainter subdorsal line; lateral area darker through being crowded with numerous irregular brownish strigulae; a row of rather conspicuous black dots on lateral area just above spiracles; spiracles whitish, ringed with blackish, small and inconspicuous; no definite markings below spiracular line.

Undersurface, legs and prolegs paler and duller, very slightly tinged with faint greenish-grey.

Thorax tolerably crested anteriorly; submedian streak not traceable; cilia of forewings whitish-ochreous, sprinkled with fuscous and blackish, of hindwings white, with indications of a grey line : all else as in L.

[2] However although variable in appearance these forms show no difference in antennae or genitalia and so, as at 2019, are not regarded as separate species.

[2] I. blenheimensis can be distinguished as even when worn and pale it has blackish forewing fringes that I. arotis lack.

[2] I. epiastra can be distinguished as it has an obvious row of black dots along the outer margin of the wing where as I. arotis is either lacks these marks or has brown dashes.

[6] This species pupates in a loose cocoon either hidden at the base of a stem of flax or on the ground.