Ilex Hairstreak - Satyrium ilicis

Scientific Name: Satyrium ilicis (Lycaenidae Lycaeninae).

English Name: Ilex Hairstreak (Blue family, Coppers and Hairstreaks sub-family).

French Name: La Thécla de l'yeuse (='Holm Oak Hairstreak').

5 Key Characters:
  • a medium sized brown butterfly.
  • adults often visit Thyme, Brambles, Privet and Dwarf Elder flowers. 
  • row of orange spots on underside of hind wing smaller than other similar species.
  • orange spots only bordered by black on the inside.
  • dashed (clearly discontinuous) white line across underside of both wings.
Lookalikes: Other Hairstreaks, but especially White-letter Hairstreak S. w-album and Black Hairstreak S. pruni (link to photo by Aigronne Valley Wildlife). The Ilex Hairstreak has less orange on the hind wing and it is bordered by black only on the inside. The white line across the underside of the wings is clearly a series of separate dashes, rather than a 'machine stitched' line like the other species.

Habitat: Hedges, woodland edges and open Oak woodland. Its French name is reflected in the fact that the species can be found associated with the large Holm Oak between the stables and the Orangerie Restaurant in the grounds of the Chateau of Chenonceau. It can be seen visiting puddles on the path in this area, in the vicinity of the toilets. It can also be found on limestone sites in the Brenne eg La Boudinière and the Bois des Roches.

Flight Period: May-June-July-August.

Caterpillar: Small and green, found in Oaks Quercus spp, especially Downy Oak Q. pubescens, more rarely in Elm Ulmus minor or Blackthorn Prunus spinosa.

Status: This is a southern species that is locally common in the Touraine Loire Valley (that is, it can be common on sites that suit it, but it is not found everywhere). It seems to be becoming increasingly uncommon in the Brenne.

Further Reading and References:
Eyes on the Hairstreaks, a blog post on Days on the Claise which talks about the function of the 'eyes' on the hind wings of most hairstreaks.

Fiche Technique - Parmi les Lycènes de France : les Théclas du genre Satyrium -- in French, with an illustrated key and details of how to tell the very similar species of the genus Satyrium apart, published by Noé Conservation, who manage several of the citizen science biodiversity projects in France.

Les Papillons de Jour de France, Belgique et Luxembourg et leurs chenilles by Tristan Lafranchis -- this is always the go to book for French butterflies. There is an English language version as well. Published by Biotope in the Parthénope Collection.

Photographed by Loire Valley Nature:

Ovipositing on Downy Oak Quercus pubescens.

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