Great Silver Water Beetle
Hydrophilus piceus
The Great Silver Water Beetle is the largest aquatic beetle in Europe, reaching lengths of up to 5 cm. It is deep black and features fine hairs on its underside that trap a layer of air, giving it a characteristic silvery appearance underwater. While the larvae are predatory and specialize in hunting aquatic snails, the adult beetles are primarily herbivorous, feeding on aquatic plants and algae.
Details
Identification
Size up to 50 mm, deep black, club-shaped antennae, long pointed keel on the ventral side of the thorax.
Social behavior
Solitary; the beetles are strong flyers and frequently move between different water bodies at night.
Diet
Larvae feed on aquatic snails; adults feed on aquatic plants, algae, and occasionally carrion.
Hunting strategy
Larvae ambush snails, seize them with their mandibles, and digest them extraorally.
Spawning substrate
A floating egg cocoon spun by the female, which is attached to aquatic plants.
Overwintering
Adult beetles usually overwinter outside the water in moist soil or under moss.
Ecology
Ecological role
Important regulator of snail populations and decomposer of plant material.
Natural predators
Waterfowl, herons, large predatory fish, and muskrats.
Competitor species
Great Diving Beetle (Dytiscus marginalis) and other large aquatic insects.
Ecosystem service
Support of the nutrient cycle in aquatic systems through herbivory and predation.
Threats
Habitat loss due to drainage, eutrophication of water bodies, and light pollution.
Scientific profile
Profile
Distinguishing features
Largest water beetle in Europe; long, sharp sternal keel on the ventral side extending beyond the hind coxae; filiform maxillary palps are significantly longer than the club-shaped antennae.