Edward Meyrick first described this species in 1883 using two specimens collected by Mr. Skellon in Blenheim and named it Cidaria triphragma.

[2] The male lectotype specimen, designated by Craw, was collected in Blenheim and is held at the Natural History Museum, London.

Forewings moderate, hindmargin strongly sinuate; pale dull greyish-purple; a very small darker basal patch, outer edge strongly convex, margined by a dark fuscous fascia, posteriorly whitish-edged; a dark fuscous fascia before ⅓, irregularly outwards-curved, posteriorly suffused, anteriorly sharply defined and whitish-edged; a minute blackish discal dot; a dark fuscous fascia beyond middle, forming a strong angle in middle, upper and lower halves both inwards-curved, anteriorly suffused, posteriorly sharply defined and whitish-edged.

[4]Although similar in appearance to H. siris, H. triphragma has larger forewings which can help distinguish it from the other species.

[2] This species inhabits native scrub in coastal, lowland and montane areas.