Idaea degeneraria, the Portland ribbon wave, is a moth of the family Geometridae. The species was first described by Jacob Hübner in 1799.
In alphabetical order:
Idaea degeneraria alticolaria (Schawerda, 1933)
Idaea degeneraria degeneraria (Hubner, 1800)
Idaea degeneraria erschoffi (Christoph, 1872)
The species has a wingspan of 26–31 mm. These small pale brown geometers are darker brown-marked between antemedian and median lines.
The larvae feed on various low herbaceous plants, mainly dandelion (Taraxacum species) and knotgrass (Polygonum species). The adults fly in one generation from June to July.
This species can be found in most of Europe, in the Near East and in North Africa. These moths prefer warm limestone undercliffs.
^ The flight season refers to the British Isles. This may vary in other parts of its range.