Idaea dimidiata

Distinguished from similar Idaea species by the combination of: single prominent discal fleck on each wing (though occasionally weak on forewings); interrupted or incomplete median band with costal stains; and the light wavy line limited mainly to the inner edge of the wing. The straw-white forewing colouration and dark marks distal to the dorsal half of the third forewing line are additional diagnostic features.

Damp locations including marshy woodland, fens, river banks, and other wet grassland habitats. Occurs across a wide range of habitats from woodland to marshes.

Holarctic. Western Palearctic: widespread in West, South and Central Europe, extending north to South Scandinavia and east to the Urals. Found on almost all Mediterranean islands; also in Morocco, Northwestern Turkey, Caucasus, Transcaucasia, North Iran, Afghanistan, and Central Asia. Nearctic: Canada and northern United States. In Britain, common and well distributed throughout England, Ireland, Wales and Isle of Man; local in southern Scotland; rarely recorded further north. British distribution has increased significantly since 1970.

Adults fly from June to August, occasionally later. Univoltine. Overwinters as larva from end of August to May.

Wild larvae feed on flowers of hedge bedstraw (Galium mollugo), cow parsley (Anthriscus sylvestris), and burnet-saxifrage (Pimpinella saxifraga). In captivity may accept herbaceous plants.

Univoltine. Eggs laid in summer. Larva overwinters from end of August to May, feeding on flower heads of host plants. Pupates in plant debris. Adult emergence June to August.

Nocturnal; adults fly at night and are attracted to light. Visits flowers between dawn and dusk during flight season. Has demonstrated ability to significantly alter phenology over 35-year period in response to increased temperatures.

• Idaea rusticataSimilar size and wing pattern, but I. dimidiata distinguished by interrupted median band with costal stains and single discal fleck pattern
• Idaea biselataOverlaps in habitat and distribution; I. dimidiata has more prominent discal flecks and characteristic costal staining

• moth
• Geometridae
• Sterrhinae
• Holarctic
• wetland
• univoltine
• climate change response

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Pyromorpha dimidiata | Beetles In The Bush
• The genome sequence of the Single-dotted Wave, Idaea dimidiata (Hufnagel, 1767).