Large blue butterflies

Large blue butterflies belong to the genus Maculinea and are members of the large butterfly family Lycaenidae. Many butterflies in this family have some sort of association with ants. Large blue butterflies have an unusual life cycle in which most of their larval life is spent as parasites inside ant nests. All large blue butterflies are rare because of this interaction with ants. There are several species of Large blue butterflies in Europe and Northern Asia. The species of large blue butterfly we study at the Universities of Copenhagen and Aarhus is the Alcon blue (Maculinea alcon). The life-cycle of the Alcon blue is shown below. Click on the small pictures or the text to see larger pictures and to find out more.


  1. The adult butterflies are on the wing throughout July.
  2. The females lay their eggs on the flowers of the Marsh Gentian (Gentiana pneumonanthe). The caterpillar hatches through the base of the egg into the flower, where it spends two to three weeks eating the flower tissue and the developing seeds. The caterpillar moults three times during this period, but stays very small (3-4 mm long, and weighing about 1-3 mg).
  3. After its third moult, the caterpillar chews a hole in the flower through which it exits. It then lets itself down from the gentian flower to the ground on a silken thread. Once on the ground it waits.
  4. If the caterpillar is found by a red ant (Myrmica species), the ant will pick the caterpillar up and take it back to its nest.
  5. Once inside the ant nest, the caterpillar will be fed by the worker ants and will probably eat a few of the ant larvae and pupae. The caterpillars will stay in the ant nest all through the autumn, winter and spring. They grow a lot during this time, reaching about 12 mm in length and weighing up to 100 mg.
  6. In the early summer the caterpillar turns into a pupa (also called a chrysalis), still inside the ant nest. The adult butterfly will emerge from the pupa about a month later. The adult has to get out of the ant nest quickly to prevent the ants killing it and leaves before its wings are expanded.

Research on the Alcon Blue at Copenhagen and Aarhus:

Population genetics

The populations of all large blue butterflies are small and fragmented. The amount of fragmentation and the migration of butterflies between populations can have major consequences for their evolution and conservation. At the University of Aarhus we are investigating the populations of the Alcon Blue butterfly in Denmark using genetic techniques. Click here to find out more.

Communication with the host ants

The caterpillars of the Alcon blue butterfly can only survive if they are adopted into an ant nest and fed by the ants. In order to do this the caterpillars have to send signals to the host ants which tell them that they should adopt and care for the caterpillars, although this is against the interest of the ants. At the University of Copenhagen we are investigating these signals, and how they might influence the ants. Click here to find out more.

Host specificity

The alcon blue is unusual among the large blue butterflies in that it uses more than one host ant species. Almost all other parasitic butterflies only exploit a single ant species. At the Universities of Copenhagen and Aarhus we are investigating how the Alcon blue is able to use different host ants, and what consequences this may have for the evolution and conservation of large blue butterflies. Click here to find out more.


Collaborations, and the EU-TMR network on Social Evolution

Much of the research at the Universities of Copenhagen and Aarhus on large blue butterflies is done in collaboration with other research groups, particularly the other members of the EU-TMR network on social evolution. Click here to learn more about these collaborations.