Coastal Silver-stiletto vs floating crystalwort

Acrosathe annulata compared with Riccia fluitans

Key Differences

Coastal Silver-stiletto is Least Concern while floating crystalwort is Near Threatened.

Taxonomic Classification

Rank	Coastal Silver-stiletto	floating crystalwort
Kingdom	Animalia (Animals)	Plantae (Plants)
Phylum	Arthropoda (Arthropods)	Marchantiophyta (liverwort)
Class	Insecta (Insects)	Marchantiopsida (Marchantiopsida)
Order	Diptera (Diptera)	Marchantiales (Marchantiales)
Family	Therevidae	Ricciaceae
Genus	Acrosathe	Riccia
Species	Acrosathe annulata	Riccia fluitans

Conservation Status

Coastal Silver-stiletto

LC — Least Concern

floating crystalwort

NT — Near Threatened

Physical Characteristics

Attribute	Coastal Silver-stiletto	floating crystalwort
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.

floating crystalwort

Habitat

Native to Asia and Europe and North America, inhabiting ecosystems characteristic of the region.

Range

Widely distributed across Asia (Taiwan), Europe (7 countries), North America (United States), and South America (Chile). 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.