[2] Its only species, Paradetis porphyrias, also known as the orange and purple fern looper, is endemic to New Zealand.

When at rest the adult has its fore-wings placed slightly backwards, the antennae extended forwards and the end of the abdomen turned upwards.

Forewings moderate, costa sinuate in middle, apex almost acute, hindmargin deeply excavated on upper half and more shortly on lower third, so as to project bluntly below middle; yellow-ochreous, irregularly mixed with brown and purplish; veins clearly marked with fuscous; two slender ochreous-brown transverse lines, dilated on costa, first before middle, bent inwards near costa, second beyond middle, almost straight; beyond second a broad purplish shade, except near costa, dilated beneath to reach hindmargin; hindmargin purple: cilia white on excavations.

[4] The species has also been found at Mount Arthur, Castle Hill in Canterbury and Lake Wakatipu.

[7][10] Hudson stated that this species inhabits ferny glens in beech forests and often can be seen in open spots in this habitat.

[13][8] Adults of this species are on the wing from December until February and fly by day with a dizzying flight close to the ground.

[7] When at rest the adult has its fore-wings placed slightly backwards, the antennae extended forwards and the end of the abdomen turned upwards.

When the fern fronds wither they turn a purplish-brown colour like the moth and it is consequently very inconspicuous and difficult to capture.