Coastal Silver-stiletto vs Common Bladderwort

Acrosathe annulata compared with Utricularia vulgaris

Key Differences

Coastal Silver-stiletto is Least Concern while Common Bladderwort is Near Threatened.

Taxonomic Classification

Rank	Coastal Silver-stiletto	Common Bladderwort
Kingdom	Animalia (Animals)	Plantae (Plants)
Phylum	Arthropoda (Arthropods)	Magnoliophyta (Flowering Plants)
Class	Insecta (Insects)	Magnoliopsida (Dicots)
Order	Diptera (Diptera)	Lamiales (Lamiales)
Family	Therevidae	Lentibulariaceae
Genus	Acrosathe	Utricularia
Species	Acrosathe annulata	Utricularia vulgaris

Conservation Status

Coastal Silver-stiletto

LC — Least Concern

Common Bladderwort

NT — Near Threatened

Physical Characteristics

Attribute	Coastal Silver-stiletto	Common Bladderwort
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Coastal Silver-stiletto

Habitat

Typically found in virtually all terrestrial and freshwater habitats.

Range

Distributed across Belgium, Denmark, Norway, and Sweden.

Common Bladderwort

Habitat

Typically found in diverse terrestrial habitats from tropical forests to temperate regions.

Range

Distributed across Belgium, Denmark, Norway, Sweden, and United States. Listed as Near Threatened, this species requires ongoing monitoring to prevent population decline.

Coastal Silver-stiletto

Coastal silver stiletto (Acrosathe annulata) is a slender robber fly in the family Therevidae, native to northwestern Europe, including the United Kingdom, France, the Netherlands, Belgium, and Scandinavia. Adults are found on coastal sand dunes and sandy heathland, where they perch on bare sand to ambush small flying insects. Stiletto flies in the family Therevidae are characterised by a slender body, long pointed abdomen, and predatory habits; adults prey on a variety of small dipterans and other flying insects during warm, sunny periods. Larvae develop in sandy soil, where they are also predatory, feeding on other invertebrate larvae. Acrosathe annulata is a habitat specialist restricted to open, sandy coastal habitats with sparse vegetation—environments that have declined substantially across northwestern Europe due to dune stabilisation, recreational disturbance, and the cessation of traditional dune management. The IUCN lists it as Least Concern, though regional conservation bodies in the United Kingdom have flagged population declines. It is considered an indicator of high-quality coastal sand dune habitats and is monitored through national invertebrate surveys.

Common Bladderwort

The common bladderwort (<em>Utricularia vulgaris</em>) is a carnivorous aquatic plant belonging to the family Lentibulariaceae. It is classified as Near Threatened on the IUCN Red List, reflecting population declines linked to habitat loss and water quality degradation. The species has been recorded across diverse terrestrial tropical to temperate habitats in Belgium, Denmark, Norway, Sweden, and the United States. <em>Utricularia vulgaris</em> is typically found in slow-moving or still freshwater bodies such as ponds, lakes, ditches, and marshes. It is rootless and free-floating, with finely divided submerged stems bearing numerous small bladder-like traps that capture zooplankton, small aquatic invertebrates, and even mosquito larvae through a rapid suction mechanism. The plant produces yellow snapdragon-like flowers on emergent stems above the water surface during summer. Its carnivorous strategy allows it to supplement nutrients in nutrient-poor aquatic environments. Biological traits of this species remain poorly documented in the scientific literature.