The eggs are deposited onto already reddish blossoms of Sanguisorba officinalis. The young caterpillars live in the flower head. In late summer the larvae are adopted by ants of the genus Myrmica and carried in the nests (especially Myrmica rubra) where they finish their development in next summer. There are also hints on larvae overwintering twice.
Maculinea nausithous colonizes mesophilous to wet meadows and fens, which are unmown from early summer to the early autumn (early or mid-June to mid-September) and host flowering plants of Sanguisorba officinalis at flight time. Maculinea nausithous is sometimes found most common in young fallows and most regularly on meadows on the edge of bogs. It can survive long on fairly small areas of less than 100 square metres, for example in the edge of ditches.
The adults occur from late June to August in one generation. Eggs are deposited into already reddish flower heads. The young caterpillar is then adopted by the host ant. Like other Maculinea species and most other Lycaenidae, they have glands, that produce a sugary secretion. The caterpillar lives then in the ant nest until the hatching of the butterfly.
Endangerment: strongly endangered
Maculinea nausithous is endangered by grassland intensification (main threat), overbuilding, drainage or succession. But measures like planting whole brooksites with bushes and trees have already eradicated many populations.
The FFH-species is very locally distributed in Western Europe (Northern Spain). Otherwise, it occurs from eastern France (here locally) across Central Europe (southern half of Germany, the Netherlands, northern Switzerland, northern Austria, Czech Republic, southern Poland, etc.) locally and parts of Asia to the Altai (Turkey, Ural, Caucasus) In Southeastern Europe, some very few local populations are known from Romania and Bulgaria.