Keeled Skimmer - Orthetrum coerulescens

Scientific Name: Orthetrum coerulescens (Libellulidae).

English Name: Keeled Skimmer (Chasers, Skimmers and Darters Family).

French Name: L'Orthetrum bleuissant (='the blueing skimmer').

5 Key Characters:
  • small to medium sized skimmer (36 - 45 mm long), about the size of one of the larger darter spp eg Common Darter Sympetrum striolatum.
  • long yellow pterostigma (the opaque mark towards the tip of the wing on the leading edge).
  • mature males have entirely pruinose (dusty blue) abdomens (no black tip) and usually brown thoraxes (not blue).
  • slender tapering abdomen.
  • face brown (never pale blue or white).
Lookalikes: Other Orthetrum spp, especially Southern Skimmer O. brunneum (but males of this species have a blue face and thorax). See this post on Days on the Claise to check out the differences between the local species of skimmer.

Habitat: Streams and flowing ditches as well as springs and seeps. Sometimes stagnant water or flooded gravel pits or quarries.

Flight Period: April-May-June-July-August-September-October-November.

Status: Widespread but localised (ie only occurring in places that particularly suit it, not everywhere and not common). It is threatened by modern ditch cleaning operations, the drying out of marshland and eutrophication of water (pollution by organic matter). On the other hand, new ditches dug to drain bogs and marshes can benefit the species temporarily.

Photographed by Loire Valley Nature:

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