This species was first described by Edward Meyrick in 1936 using a specimen bred by George Hudson from a larva collected at Arthur's Pass.

[4] Hudson discussed and illustrated both the adult male and female in his 1939 book A supplement to the butterflies and moths of New Zealand.

The whole effect is extraordinarily protective when the larva is resting on its food plant, mountain tauhinu (Cassinia vauvilliersii).

Fore-wings subtriangular, termen rather obliquely rounded; brownish-ochreous, transversely strigulated dark fuscous; lines waved, whitish, internally strongly edged dark fuscous, first from costa at 1⁄5 to dorsum at 1⁄3, excurved, second from costa at 3⁄5 to dorsum at 2⁄3, rather excurved in disc but indented or excised above middle, followed in ♂ by broad whitish-ochreous suffusion on costal and dorsal thirds, subterminal nearly parallel to termen, obsolete in middle, in ♀ with an enlargement above this, connected with termen beneath apex by a white dash; discal spot transverse, dark fuscous, inconspicuous; a terminal series of small blackish spots or marks: cilia yellow-whitish irregularly suffused grey.

[5] Hudson pointed out that this species resembles P. productata but differs from it as P. colpogramma's antennal pectinations are slightly shorter and has distinctive dark grey subterminal spots on the hind-wings.

[1] Other than the type locality, this species has been observed in the Tasman, North Canterbury and Otago regions.