The two species share habitat and possess similarities, but, among other visual differences, P. nielseni is smaller and has significantly more sheen to its forewings than P. cupreus.

The scales on the forewings of both sexes are brightly metallic, usually golden and green, giving the moth a brilliant sheen.

Females lay pale yellow eggs on the small flowering shrub Hibbertia spicata, ovipositing singly on the leaves, sepals, or stems.

The brightly coloured larvae feed on the plant and afterwards pupate in silken cocoons on leaves or stems, or in leaf litter on the ground.

[1] In the subfamilies Procridinae and Zygaeninae of the family Zygaenidae, female moths typically have two glands near the ovipositor that produce liquid poison.

A tuft of hair at the end of the female's abdomen is brushed over each egg after it is laid, thereby attaching small spiny scales to its surface.