Mating of Maculinea nausithous
Source: André Künzelmann, UFZ

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Marsh area near Leipzig, Germany / Habitat for Large Blue butterlies
Source: André Künzelmann, UFZ

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The great burnet Sanguisorba officinalis. Maculinea nausithous and teleius need the great burnet to lay their eggs on the leaves.
Source: André Künzelmann, UFZ

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It appears to be a dilemma with no way out: if farmers mow their meadows in May and August, as they have done up till now, the Large Blue butterflies (Maculinea nausithous and teleius) stand no chance of survival. This is because these butterflies lay their eggs on the great burnet (Sanguisorba officinalis) in July. The caterpillars that emerge from the eggs have specialised on this plant. If this plant is not present, the Large Blues have no chance to lay their eggs. However, if the hay is not cut at all, the meadow becomes overgrown and the black-backed meadow ants (Myrmica) cannot survive. Yet the Large Blues need them too because it is the ants that ensure that the caterpillars survive and turn into butterflies the following summer – butterflies that lay eggs and reproduce. The caterpillars of the Large Blues use a chemical trick to get the ants to carry them into their nests, occasionally feed them like a cuckoo and bring them through the winter.
The solution: meadows in which rare butterflies are found should ideally be mown late – in September – and then only every two years. However, other mowing systems could also allow the Large Blues to survive, although to a lesser extent. But lower yields and poorer quality hay mean losses for the farmer. The scientists at the UFZ will therefore use their software to calculate case by case how many compensation payments would be necessary to win over farmers to butterfly-friendly farming. The implementation of the European Habitats’ Directive forces countries to establish management plans over the next few years for the protection of endangered species.
This dual dependence on the right plant and the right species of animal makes the Large Blues so interesting to science. Since it reacts very sensitively to environmental influences, scientists can use it as an alarm signal. Where Large Blues disappear, nature changes too and other species are threatened. This means that the butterflies – like all butterflies in principle – act as bioindicators.
Indicator species like these are a part of the MacMan research project, which has been studying the protection of habitats for endangered animal and plant species over the past four years. This research project received EU funding of 3 million Euros and was led by the UFZ. Basing their research on butterflies that occur in large areas of Europe and yet face a serious threat of extinction, the team investigated the factors that lead to the decline of species and the possible countermeasures. At the beginning of December, over 150 scientists from 20 countries met in Leipzig to discuss the results of the research project.
Tilo Arnhold