Banded Demoiselle
Calopteryx splendens
The Banded Demoiselle is a large damselfly known for its striking metallic blue-green coloration. Males feature characteristic dark bands across their wings, while females are typically metallic green with translucent wings. It primarily inhabits slow to moderately flowing streams and rivers with abundant aquatic and riparian vegetation.
Details
Identification
Males with a broad, blackish-blue band across the center of the wings; females with greenish-translucent wings and a white pterostigma; bodies of both sexes with a metallic luster.
Social behavior
Males occupy territories on bank vegetation and defend them aggressively against rivals; distinct courtship behavior including hovering flight.
Diet
Adult damselflies hunt small flying insects; larvae are predatory, feeding on other insect larvae, small crustaceans, and worms.
Hunting strategy
Perch-and-wait predator; prey is spotted from a lookout and captured in flight.
Spawning substrate
Endophytic egg-laying into the tissue of aquatic plants, often into floating leaves of pondweeds or bur-reeds.
Overwintering
Overwintering occurs in the larval stage within the sediment or attached to aquatic plants on the water bed.
Ecology
Ecological role
Important predator in aquatic and terrestrial boundary habitats; serves as food for birds, fish, and larger insects.
Natural predators
Birds (e.g., wagtails, kingfishers), larger dragonfly species, orb-weaver spiders; larvae are eaten by predatory fish.
Competitor species
Beautiful Demoiselle (Calopteryx virgo), though C. splendens prefers more open, slower-moving sections.
Ecosystem service
Biological pest control by consuming mosquitoes and other insects; indicator of water quality.
Threats
River engineering, pollution from pesticides and fertilizers, intensive riparian mowing, desiccation due to climate change.
Scientific profile
Profile
Distinguishing features
Males possess a characteristic blue wing band (unlike C. virgo, where almost the entire wing is blue). Females have a white pseudopterostigma located closer to the wing tip than in C. virgo.
Role in food web
Secondary consumer; important link in aquatic and terrestrial food webs as both predator and prey.
Protection & threats
Main threats
River engineering, intensive maintenance (weed cutting), eutrophication from agriculture, loss of riparian buffer strips, and excessive shading by dense riparian woody plants.
Population trend
Stable to increasing; the species has benefited from improved water quality in Central Europe over recent decades.
Conservation measures
Revitalization of flowing waters, creation of riparian buffer zones, reduction of nutrient inputs, gentle water body maintenance (sectional mowing).