Maculinea alcon, the Alcon Large Blue Butterfly, thrives in moist heathland In which the caterpillar's foodplant, the Marsh gentian (Gentiana pneumonanthe), and red ant nests of Myrmica ruginodis or M. scabrinodis are present. The presence of the butterfly together with host ants, full-grown Marsh gentians and gentian seedlings is an important indication of the quality of the ecosystem and its management. Seeds of the Marsh gentian only germinate under conditions of high moistness of the soil, sufficient light and a relatively high temperature. The most favourable type of management is small scale sod-cutting. However, it should be taken into account that it takes ten years before the sod-cutted areas are well colonized by ants again. Mowing (in September or later) is a good alternative. Grazing of heathlands must be carried out in a very extensive way to minimize grazing damage to gentians and trampling effects on ant nests.