Treasure of the month March: The spider-shaped snow gnat

4 March 2019

Photo: UHH/CeNak, Thure Dalsgaard

Spider-shaped snowflies are counted as flies, even though they do not have wings.

Searching for a seven millimeter tiny insect in the midst of large boulders is a bit like trying to find a needle in a haystack. Robert Klesser, an entomologist at LIB, has made it his mission to explore the fauna of the tiny inhabitants of so-called boulder piles. On one of his crawls through the boulders, he came across the spider-shaped snow gnat (Chionea araneoides). This wingless midge is our treasure of the month March.

The spider-shaped snow gnat (Chionea araneoides) from the family of wagtails (Limoniidae) likes it cold. That is why it is active exclusively in winter, as its name suggests. In Germany, it can only be found in the last boulder dumps of the low mountain ranges, where in summer it can retreat into the depths of the winding cave system under the boulders. This is because there are ice cores inside the dump that originated in winter, and the cool temperatures under the boulders prevent them from melting completely even in summer, creating a unique cold air system. Some of these ice blocks may date back to the last ice age.

Where to find the snow gnat

At that time, the spider-shaped snow gnat was probably widespread throughout Central Europe, but it retreated more and more as the climate warmed and is now found mainly in the high elevations of European mountains. Large populations of this small mosquito, which feeds on plants, are still found in Russia and some countries in Eastern Europe, as well as the Alpine region and Scandinavia. In 2009, it was discovered in Germany for the first time. After the Fichtelgebirge, insect specialists also found it in the Harz Mountains, the Rhön Mountains and the Bavarian Forest.

Exploring the log pile habitat

Robert Klesser, who received the German Wildlife Foundation's research award in 2017 for his studies at CeNak, is researching the populations of various animal species that call log heaps home in his doctoral thesis "New bugs on the block." Using cup traps and physically climbing among the rocks, he sets out to find the tiny inhabitants of this complex and intricate ecosystem. He then takes the animals he collects to CeNak in Hamburg, where he studies them genetically. "Since the populations have probably been geographically isolated from each other for thousands of years, mutations can be used to find out where these populations originally came from, how they were distributed and how big they were now and then, how old they are and whether they are on their way to becoming new species," the biologist says of his work.

Endangered ecosystem

And his work is important. Because the log pile habitat is far from being explored, and yet it is already endangered again. For example, through increasing nutrient inputs, which promotes unloved vegetation that settles in the crevices between the boulders and brings cold air currents to a standstill until the block dumps are completely overgrown. Tourism in the mountain regions can also upset the balance of the sensitive ecosystem. Once the last refuges have disappeared, so do their unique inhabitants. Research helps to understand these habitats and develop measures to preserve them.

Learn more about log piles and the project at Deutschen Wildtierstiftung.