This species was first described by Edward Meyrick in 1883 using two specimens collected at Taranaki and Wellington in January and February and named Semiocosma prasophyta.

[4] In 1928 George Hudson followed this placement and discussed and illustrated this species under the name Izatha prasophyta.

[6] The male lectotype, collected at the Wellington Botanic Garden, is held at the Natural History Museum, London.

Forewings moderate, costa gently arched, sinuate in middle, apex obtuse, hindrnargin slightly sinuate, oblique; whitish, irrorated and partially suffused with dull ochreous-green, especially on central third and towards hindrnargin; extreme base and an irregular streak from costa near base to base of inner margin black; a small cloudy blackish spot on costa before middle, and another beyond middle; two tufts of green scales in disc before middle, followed by scattered black scales, and two tufts beyond middle, preceded and followed by black scales; a clear whitish sinuate transverse line from 3⁄4 of costa to before anal angle; three black dots on posterior third of costa, and an interrupted black hindmarginal line : cilia fuscous, with a cloudy blackish line.

[6] This species is endemic to New Zealand and it is found throughout the North Island with the exception of the Hawkes Bay and the Wairarapa.

[6][5] When resting the adult holds its wing flat and slightly overlapping and its antennae close to its body.