Besma quercivoraria

Distinguished from similar geometrid moths by combination of: sexual dimorphism in adults, specific wing patterning associated with oak besma, and phenology varying by region (two generations per year with southern populations active April–September, northern populations May–August).

Sexually dimorphic adults with wingspan 27–41 mm. Males and females differ in appearance.

Associated with deciduous and mixed forests containing host trees including oak, elm, poplar, willow, birch, and spruce.

Southern Canada from Newfoundland to British Columbia; contiguous United States except California. Present in Alberta, Manitoba, Saskatchewan, and Vermont.

Two generations per year. Adults active April–September in southern range, May–August in Ontario, late May–July in Alberta.

Larvae feed on leaves of oak (Quercus), elm (Ulmus), poplar (Populus), willow (Salix), white spruce (Picea glauca), and paper birch (Betula papyrifera). Paper birch is the primary host in southern Canada.

• Quercus - larval food plant
• Ulmus - larval food plant
• Populus - larval food plant
• Salix - larval food plant
• Picea glauca - larval food plant
• Betula papyrifera - larval food plantPrimary host in southern Canada

Two generations per year (bivoltine). Adult flight period varies by latitude: April–September in south, May–August in Ontario, late May–July in Alberta.

Larval herbivore on broadleaf and coniferous trees; contributes to nutrient cycling in forest ecosystems through leaf consumption.

• Other Besma speciesSimilar wing patterns and body form; requires examination of genitalia or specific wing markings for definitive identification
• Other Ennominae geometridsShared family characteristics; oak besma distinguished by host association, sexual dimorphism, and phenological pattern

• geometrid moth
• sexual dimorphism
• bivoltine
• forest pest
• polyphagous

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life