Very similar in size and appearance to the Ashen Wave (Idaea deversaria). It lacks small black dots in the wing fringes, usually present in Ashen Wave. Other subtle differences are described in Hausmann (2004), The Geometrid Moths of Europe, Volume 2. Perhaps best separated by genitalia dissection.
This species also closely resembles the f. remutata form of Riband Wave, but is slightly smaller. Its smooth, rather silky, muddy-brown wings and fainter cross-lines help distinguish it (Waring et al,(2017), Field Guide to the Moths of Great Britain and Ireland). The third cross-line is not kinked at the leading edge as it usually is on the Riband Wave.
Pupates in plant debris.
Open woodland, scrubby heathland, hedgerows and gardens.
There are no records in the system yet in Bulgaria.