The adult moths have been observed on the wing all year round but are most commonly seen from November until February.

[2] Hudson described the larva of this species as follows: slightly over 1⁄2 inch in length, rather stout, green, paler underneath, with the skin slightly wrinkled; the head is ochreous; there is a broad dull crimson dorsal line containing a central black bar on each segment; two or three rows of conspicuous black warts emitting short black bristles, and a very indistinct greyish lateral line.

[6]Robert Hoare pointed out that white stripe along the back of the larva helps camouflage it as it resembles the leaf vein on the leaves on some of its host plants.

All the wings arc pale yellow with a variable number of fine jagged reddish-brown transverse lines, which are usually most distinct towards the termen.

[11] Larvae are active and feed on the leaves and seeds of their host plants during the New Zealand spring and summer.

[13][6] Adult E. undosata feed from the flowers and assist with the pollination of Dracophyllum acerosum, Hoheria lyallii, and Veronica salicifolia.