Mercury Bluet – Southern Damselfly – Coenagrion mercurial – UK – European Dragonfly photo

The Mercury Bluet – Southern Damselfly ( Coenagrion mercuriale ) is a rare species in the UK although it is less scarce in France, Spain and Italy but it is confined to Western Europe and the Northern Maghreb. It is quite a small blue damselfly at 27-31 mm and has particular habitat requirements, needing open sunny and often alkaline seepages and streams. The New Forest habitat shown below is one of the best known sites in the UK where calcareous water emerges from heathland to form running rivulets full of submerged plants. It is a species which is declining through most of its range due to changes in agricultural practice such as less animal grazing to maintain open bank edges and also to poorer water chemistry.

KEY I/D FEATURES :

Males have a characteristic mark on Segment 2 of the abdomen which is shaped like a horned helmet as depicted by the Roman God Mercury – so giving rise to the name Coenagrion mercuriale. The pterostigma have light edges and a dark centre.

Females have abdomens with extensive black top markings with blue beneath.