Carsia sororiata

Distinguished from similar geometrids by the combination of two wide forewing cross lines with the characteristic bent outer line bearing two outward-pointing spikes. The 'bridge' formed where the two lines connect in the posterior wing half, when present, is diagnostic. Subspecies imbutata (Central Europe) is additionally marked by reddish-brown suffusion in the distal wing field. Separation from related Carsia species requires examination of genitalia.

Northern and central Europe; Urals; Siberia; Russian Far East; northern Mongolia; North America from Alaska to Newfoundland and south to New Hampshire. GBIF records confirm presence in Alberta, Manitoba, and Saskatchewan, Canada.

Adults on wing July to August. Single-brooded.

Larvae feed on Vaccinium uliginosum, V. oxycoccos, V. myrtillus, and Rubus arcticus.

Egg initially whitish yellow, becoming deeper yellow; micropylar rosette 8-leaved with irregular reticulation. Larva stout, uniform thickness, dorsal surface deep brownish-red with fine blackish-red dorsal and subdorsal lines, broad bright yellow lateral stripe with red spots at folds between middle segments, venter pale greenish yellow with paler dark-edged central line. Pupation details not documented.

Larval herbivore on Ericaceae and Rosaceae shrubs in boreal and montane habitats.

• Other Carsia speciesGenitalia examination required for definitive separation
• Subspecies imbutata vs. nominate sororiataImbutata distinguished by reddish-brown distal wing suffusion and more variegated pattern with distinct sub-basal line and two median bands

• geometrid
• moth
• Holarctic
• boreal
• Vaccinium feeder
• single-brooded
• wing pattern polymorphism

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Platystomatidae | Beetles In The Bush