The Great Predatory Ground Beetle (Calosoma sycophanta), with its shiny blue-metallic pronotum and golden shimmering elytra, has been sighted again in Southern Bavaria. The insect measures between 17 and 28 millimeters in length. Recent discoveries were made in the oak forests northwest of Munich, as well as in Bogenhausen, the Freising area, and in Landshut.
For biologist Stefan Müller-Kroehling of the Bavarian State Institute for Forestry and Forestry (LWF) in Freising, this is an encouraging find. “The name sounds aggressive, but this beetle is an extremely helpful ally in the forest. It should actually be called the ‘caterpillar hunter,’ because butterfly caterpillars and their pupae are its favorite prey, which it devours with great appetite. Videos show how it boldly invades large caterpillar nests like a predator attacking a group of prey,” he said.
Great Predatory Ground Beetle Plays Important Role in Controlling Caterpillar Infestations
While the Great Predatory Ground Beetle has reappeared in recent years in Northern Bavaria, where the hot weather has caused outbreaks of gypsy moths and oak processionary caterpillars, it remained absent in the south for a long time. These caterpillar species severely damage oak and hornbeam trees by feeding on their leaves. Affected trees may become so weakened that they die. Additionally, the toxic hairs of oak processionary caterpillars can cause allergic reactions in humans. In some regions, their infestation has reached such extreme levels that forests have become temporarily inaccessible, according to Müller-Kroehling.
Henrik Hartmann from the Julius Kühn Institute in Quedlinburg confirmed that climate change is the reason for the massive spread of these caterpillars. Müller-Kroehling added that the Great Predatory Ground Beetle has returned to these areas as their natural enemy in response to these changes.
Unusual Sightings as Individual Beetles Appear in Unexpected Regions
From time to time, individual beetles are found far from their preferred habitats, such as in Frankfurt am Main or the Gäuboden area. For Müller-Kroehling, this remains a fascinating natural phenomenon. “It is remarkable that the Great Predatory Ground Beetle can track down its prey so precisely from Southern Europe or Southern France,” he noted.
For decades the species remained undetected, only to suddenly reappear during large caterpillar outbreaks. Its flights even take it across the Alps to altitudes of up to 2,000 meters. It has also crossed the English Channel and has even been spotted on oil rigs. Thanks to its strong flight muscles, which remind experts of a “football player,” it is well equipped for long journeys.
How to Identify the Great Predatory Ground Beetle: Key Features and Similar Species
The Great Predatory Ground Beetle is easily recognized by its green-gold shimmering body and noticeably long legs. A distinctive feature is its transversely oval, metallic blue pronotum. Viewed from above, the body appears pinched behind the pronotum due to its narrow waist. This detail sets it apart from similar species: the Golden Ground Beetle also shines golden but has a more rectangular pronotum. The Rose Chafer also has a metallic sheen but appears stockier, with a pronotum that narrows forward into a triangular shape.
Native and Beneficial, Not Invasive
The Great Predatory Ground Beetle is not an invasive species but belongs to the native beetle fauna that was present during earlier warm periods. For Müller-Kroehling, its return is a positive sign. “It shows that not only pests are spreading, but also their natural enemies. Such southern European species should be welcomed in our region,” he remarked.
Breeding these beetles for deliberate release is hardly feasible, as their larvae must be raised individually to prevent them from eating each other. Nevertheless, Müller-Kroehling sees positive prospects for forest managers. “Wherever there is a major caterpillar outbreak, the Great Predatory Ground Beetle will find it. It is strong and capable of flying far enough,” he said.
Public Asked to Report Sightings of the Great Predatory Ground Beetle
To learn more about the distribution and behavior of this species, Müller-Kroehling has asked the public to contribute: anyone who spots a Great Predatory Ground Beetle should send a photo, including the date, exact location (address or GPS coordinates), a brief description (“forest path,” “terrace,” etc.), and the beetle’s condition (alive, flying, dead) to:
📧 puppenraeuber@lwf.bayern.de
The recent discoveries in Southern Bavaria—the first since 1906—also came from such citizen reports. Müller-Kroehling plans to publish all submitted sightings on an online map soon. The goal of this citizen science project is to encourage more people to engage actively with their local natural environment.
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