Margined Ground Beetle
Agonum marginatum
The Margined Ground Beetle is a ground beetle species measuring approximately 8 to 10.5 mm in length, characterized by its metallic green to bronze upper surface and a distinct yellow margin on the elytra. It primarily inhabits open, moist habitats such as riverbanks, mudflats, and marshes. The species is widely distributed across Europe and is considered a typical inhabitant of pioneer sites near water bodies. It is an agile predator, particularly active on sunny days when it can be seen running across sparsely vegetated ground.
Details
Identification
Metallic green pronotum and elytra; broad, light yellow to whitish margin on the outer sides of the elytra; legs partially light-colored.
Social behavior
Solitary, but often occurs in larger groups on shore sections under optimal conditions.
Diet
Predatory diet consisting of small invertebrates such as insect larvae, mites, and worms.
Hunting strategy
Active searching and chasing of prey on the ground using visual perception.
Spawning substrate
Moist soil or mud near shorelines.
Overwintering
Overwintering occurs as an imago (adult beetle) in the soil or under plant debris.
Ecology
Ecological role
Important predator in semi-aquatic transition zones; regulates small animal populations on the shore.
Natural predators
Insectivorous birds, amphibians (e.g., frogs), and larger predatory arthropods.
Competitor species
Other hygrophilous ground beetle species such as Agonum muelleri or Bembidion species.
Ecosystem service
Pest control through predation of small invertebrates.
Threats
Loss of natural riparian habitats due to construction, drainage of wetlands, and heavy shading caused by succession.
Scientific profile
Profile
Distinguishing features
The most important feature within the genus Agonum is the broad, yellow lateral margin of the elytra. The pronotum is heart-shaped, significantly narrower than the elytra, and rounded at the posterior angles. The antennae are pubescent from the fourth segment onwards. Compared to Agonum sexpunctatum, it lacks deep pits on the elytra, and the yellow margin is diagnostic.
Habitat
Hygrophilous species preferring open, sunny riparian zones of standing or slow-flowing waters. It is found on muddy and sandy banks, in gravel pits, at the edges of ponds, and in wet meadows with sparse vegetation.
Diet
Zoophagous; both adults and larvae are predatory, feeding on small invertebrates such as insect larvae, mites, and small worms.
Role in food web
Important predator in semi-aquatic transition zones; serves as prey for birds (e.g., waders), amphibians, and larger predatory arthropods.
Protection & threats
Main threats
Loss of dynamic riparian habitats due to river engineering, drainage of wetlands, and the abandonment of gravel pits (succession).
Population trend
Classified as stable and not threatened overall in Germany, though locally declining due to habitat loss.
Conservation measures
Protection and restoration of watercourses and their floodplains; promotion of natural dynamics on banks; preservation of secondary habitats such as gravel pits.