Dusky large blue


Maculinea nausithous


A small butterfly in the Lycaenidae family, I have a wingspan of about 18 mm. The underside of my wings is identical for males and females of my species: chocolate or cinnamon-brown with a single row of black dots.   The top of my wings is blue bordered by a wide brown band on the males and uniformly brown on the females.



I feed on nectar from flowers.


I lay my eggs in the inflorescences of the Sanguisorba officinalis, my host plant. Three weeks after hatching, my caterpillar crawls down the stem to the ground. At this point, the survival of my species depends on one species of ant: Myrmica rubra. These ants will lead my caterpillar into its nest where it secretes a sweet substance that attracts the ants. Once in the ant nest, my caterpillar feeds on its host’s brood until it has fully developed and it flies away the following summer.


I live for about 10 days as an adult.

Where and when can you find me in the reserve ?


I live in wet meadows where my host plant, the Sanguisorba officinalis, grows.

When to spot me

You can find me between mid-May and mid-August.

Mistaken identity

You can find me from late June to early September.

Conservation status

  • Red list of Rhopalocera in metropolitan France: Vulnerable (VU).
  • Red list of endangered Rhopalocera and Zygaena in Alsace: Vulnerable (VU).
  • Protected in France

Over a hundred species referenced