Insect of the Year

Since the "Insect of the Year" board of trustees was established in 1999 – primarily by the then director of the German Entomological Institute, Prof. Dr. Holger Dathe – this commission selects each year an insect species that should enjoy greater fame because of its special importance for the ecosystem, its particular rarity, its aesthetic value or even its "ordinariness".

The Insect of the Year is intended to bring an exemplary species (and insects in general) closer to people. Well-known entomologists, representatives of research institutions and nature conservation organisations from Germany, Austria and Switzerland together make an important and difficult decision, the choice among about one million described insect species (even if "only" about 35,000 of them occur in Germany) and select the species that is to represent the inconspicuous and yet so important "creepy-crawlies" among humans for a whole year.

Insect of the year 2021: The Danish Mayfly

A Danish Mayfly (Ephemera danica) © Wolfgang Kleinsteuber

They have existed for about 355 million years: mayflies. But today only about 140 species live in Central Europe. "The Danish mayfly Ephemera danica, a representative of a very ancient group, is the 'insect of the year'. These animals, which are between one and two centimetres long, are widely distributed in Europe and colonise a wide range of waters - from the smallest streams to large rivers. What makes the mayfly unique is its life cycle: from the egg laid in the water to the insect capable of flight and mating, which dies after a few days," says Prof. Dr Thomas Schmitt, Director of the Senckenberg German Entomological Institute in Müncheberg and Chairman of the Board of Trustees, explaining the choice.

The developmental cycle of the insect, which can be recognised by striking black spots on its wings of about two centimetres in length, begins with the laying of eggs in the water. Between May and September, the females of the Danish mayfly fly over the water on a zigzag course, repeatedly dipping the tip of their abdomen into the water. In this way, they lay several thousand eggs in portions, which then sink from the bottom of the water, where they get stuck with their sticky outer shell.

The larva of the Danish mayfly develops over one to three years into a flyable insect. © Wolfgang Kleinsteuber

After a few days, the larvae hatch, which initially breathe through the skin. As they grow, they repeatedly shed their skin and develop clearly visible gills.

At 20 to 30, the number of these moults is very high compared to other insect orders. Buried in the fine-gravelly to sandy-silty bottom of the river bed, the larvae take one to three years to develop, depending on various environmental factors such as water temperature or food supply.

The subimago of the Danish Mayfly © Wolfgang Kleinsteuber

"Shortly before the transition from aquatic to terrestrial life, a layer of air forms between the old and new skin of the adult larvae. By reducing its specific weight, the larva rises to the water surface. Once there, the larval skin bursts and within a few seconds a flyable mayfly hatches," adds Schmitt. However, this is not yet capable of reproduction, for which the insect still needs one last moult. The fully developed mayfly has neither mouth parts nor a functioning intestine. Therefore, time is pressing: Only a few days remain before the animals die for mating and oviposition.
"Fortunately, there is no acute danger for our 'insect of the year 2021'. However, due to its special development cycle, the Danish mayfly is dependent on ecologically intact waters with sufficient oxygen content", explains Axel Vogel, Minister of Agriculture, Environment and Climate Protection of the State of Brandenburg and this year's patron of the "Insect of the Year", and continues: "Comprehensive water protection with the promotion of natural water body structures is therefore one of our goals - this is the only way we can protect the Danish mayfly and many other organisms!"