The Downy Emerald (Cordulia aenea) is a dragonfly within the family of Emerald Dragonflies (Corduliidae).
The Downy Emerald (47-55 mm) is the only species of its genus in Europe.
Like most other emeralds, the Downy Emerald has bright shiny green eyes.
In Europe, it can easily be confused with the Brilliant Emerald (Somatochlora metallica) and, in eastern Europe, with the Balkan Emerald (Somatochlora meridionalis), which usually have a more obvious metallic green body and have yellow markings on the face.
In addition, the male Downy Emerald has a more strongly club-shaped tail than the male Brilliant Emerald.
The female Downy Emerald can be distinguished from the female Brilliant Emerald by having a much smaller ovipositor (near segment 8).
The ovipositor of the female of the Brilliant Emerald is rather large and sticks out in a 90 degree angle.

Naardermeer, Naarden, The Netherlands, 26 April 2014