The largest and darkest Calopteryx, with (almost) entirely metallic cobalt wings in males and transparently greenish to deep ebony wings in females. The flight is butterfly-like.
Total: 45-49 mm.
Abdomen: 31-42 mm.
Hindwing: 24-36 mm.
Prefers cooler running waters than other Calopteryx, typically smaller, more shaded or at higher latitudes: small forest streams are the classic habitat.
From May to August.