Large Blue - Maculinea arion

Scientific Name: Maculinea arion (syn Phengaris arion, Glaucopsyche arion).

English Name: Large Blue.

French Name: L'Azuré du serpolet (='the thyme azure').

5 Key Characters:
  • very large for a Lycaenidae (Blue) butterfly.
  • no orange markings.
  • underside of hindwing usually has blue basal flush.
  • 'ladder' pattern on the underside fringe quite pronounced.
  • black spots very bold.
Lookalikes: Scarce Large Blue M. telejus, which has smaller spots. Alcon Blue M. alcon, which has much less pronounced laddering and the spots on the upperside are obscured.

Habitat: Dry closely grazed grassland, unimproved grassland, grassy fallow areas, flower rich field margins invaded by Oregano, woodland edges and open woodland.

Flight Period: June-July-August.

Caterpillar: Small and cream coloured, tended by the ant Myrmica sabuleti and overwintering in the ant nest. September - June. The caterpillars eat the ant larvae.

Host Plant: Thymes (Large Thyme Thymus pulegioides, Creeping Thyme T. praecox), Oregano Origanum vulgare.

Status: The poplulation dropped by 50% between 1990 and 2007, but the current trend is uncertain - probably still declining. It is a Grassland Indicator Species (one of the butterfly species which are monitored to give some idea of the overall health of natural grasslands). In the Touraine Loire Valley and Brenne it can be quite abundant but localised. Red Listed and protected Europe wide. At the Chateau de Taillé Vacation Centre at Fondettes, just outside Tours, there is a project to recreate habitat suitable for the butterfly (the first in France) and reintroduce the species to the site. It still occurs on several well-known nature reserves such as the Puys du Chinonais and the Epéron de Murat at Ferriere Larcon, as well as on unimproved grasslands in the Claise and Creuse Valleys (although it is threatened here by development). Populations using Oregano as their host plant seem to be more robust and tolerate denser vegetation than those using Thyme.

Further Reading and References:
Les Papillons de jour de France, Belgique et Luxembourg et leurs chenilles by Tristan Lafranchis.
European Butterflies: a portrait in photographs by Brian Watts.
A post on our daily blog Days on the Claise about the species.

Photographed by Loire Valley Nature:
All photos will enlarge in a new window if clicked on. Row 1 left & centre nectaring on brambles on the edge of the Parc de Boussay, June.

On the larval host plant, Wild Oregano Origanum vulgare.

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