Idaea dilutaria, also called the silky wave, is a moth of the family Geometridae. It is found in Europe.

The species has a wingspan of 20–22 mm.Recognizable by its strongly silky gloss, the absence of costal colouration (the costal margin has merely a sparse dusting of dark scales), the unmarked distal margin and fringe.The ground-colour is yellowish-tinted the discal dots are minute and there are no terminal lines.The other lines are generally all of approximately equal expression, sometimes the postmedian a little stronger, sometimes the median of the forewing weak.The underside is similar, the postmedian line often a little stronger, theantemedian and sometimes the median of the forewing obsolete. The males antennal ciliation is short and even.

The adults fly in one generation in July ^[1].

The larvae feed on Helianthemum nummularium.

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