It inhabits native forest at lower altitudes and its larval host are moss species in the genus Racomitrium.

This species was first described by Robin C. Craw in 1987 using specimens collected in Riwaka by Alfred Philpott.

This species was described by Craw as follows:Small to medium sized (9.5-13.1 mm) triangular forewing.

[2]This species is similar in appearance to and can be easily confused with H. alba and H. cinerearia.

[5] H. mutabilis is associated with lower altitude forests of Nothofagus and podocarp species.