Cupido amyntula

(Boisduval, 1852)

Western Tailed-Blue

Species Guides

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Cupido amyntula, commonly known as the Western Tailed-Blue, is a small in the Lycaenidae found across western North America. Males display blue upperside wing coloration while females are darker brown with a brown band on the outer wing. The has a wingspan of 2.2 to 2.9 cm and is distinguished from similar species by the presence of tail-like projections on the hindwings.

Cupido amyntula by (c) Matt Benotsch, some rights reserved (CC BY), uploaded by Matt Benotsch. Used under a CC-BY license.Cupido amyntula by (c) Nick Block, some rights reserved (CC BY), uploaded by Nick Block. Used under a CC-BY license.Cupido amyntula 'Western Tailed Blue' by Doug Waylett. Used under a CC BY 2.0 license.

Pronunciation

How to pronounce Cupido amyntula: /kʊˈpiːdoʊ əˈmɪntjʊlə/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from Cupido comyntas (Eastern Tailed-Blue) by geographic range—C. amyntula occurs in western North America while C. comyntas is eastern. The two overlap minimally. Tails on hindwings separate both from tail-less blues in Celastrina. Underside spotting pattern and wing proportions differ from similar Lycaenidae.

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Appearance

Small with wingspan 2.2–2.9 cm. Male upperside blue; female upperside darker brown with brown band on outer wing. Underside grayish with scattered black spots. Hindwings possess short, delicate tail-like projections near the lower margin.

Habitat

Open including grasslands, meadows, forest edges, and disturbed areas. Associated with larval plant distribution.

Distribution

Western North America from Alaska southward through western Canada and United States. Records from Vermont suggest possible eastern occurrences or vagrancy.

Seasonality

fly spring through summer, with multiple in warmer portions of range. Timing varies by latitude and elevation.

Diet

Larvae feed on leguminous plants: Thermopsis, Astragalus, Oxytropis, Vicia, and Lathyrus . nectar at flowers.

Host Associations

  • Thermopsis - larval
  • Astragalus - larval
  • Oxytropis - larval
  • Vicia - larval
  • Lathyrus - larval

Life Cycle

Complete with , larva, pupa, and stages. Larvae feed on plant foliage. occurs in leaf litter or soil. Multiple per year in favorable climates.

Behavior

perch with wings closed, showing spotted undersides. Rapid, low when disturbed. Males patrol for females in suitable .

Ecological Role

as . Larval herbivore on legumes. Prey for birds, spiders, and other .

Human Relevance

Subject of citizen science observation (6326 iNaturalist records). for grassland quality. No significant economic impact.

Similar Taxa

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Taxonomic Note

Some authorities place this in Elkalyce as Elkalyce amyntula. GBIF lists Cupido amyntula as a synonym of Elkalyce amyntula, though Cupido remains widely used in North American literature.

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