Although similar in appearance to Helastia corcularia, H. salmoni can be distinuished as its forewings are a lighter white-grey.

This species was first described by Robin Craw in 1987 using specimens collected at the Homer Tunnel and at Gertrude in Otago.

[3] The male holotype, collected at the Homer Tunnel in January by John T. Salmon, is held at Te Papa.

Upperside forewing whitish-grey with wavy brown transverse lines.

[3]Craw went on to explain that this species can be distinguished from Helastia corcularia as H. salmoni has forewings the upper side of which is coloured white-grey whereas H. corcularia has a darker more slate grey colour.