Coastal Silver-stiletto vs River Thread-moss

Acrosathe annulata compared with Bryum riparium

Key Differences

Coastal Silver-stiletto is Least Concern while River Thread-moss is Vulnerable.

Taxonomic Classification

Rank	Coastal Silver-stiletto	River Thread-moss
Kingdom	Animalia (Animals)	Plantae (Plants)
Phylum	Arthropoda (Arthropods)	Bryophyta
Class	Insecta (Insects)	Bryopsida (Bryopsida)
Order	Diptera (Diptera)	Bryales (Bryales)
Family	Therevidae	Bryaceae
Genus	Acrosathe	Bryum
Species	Acrosathe annulata	Bryum riparium

Conservation Status

Coastal Silver-stiletto

LC — Least Concern

River Thread-moss

VU — Vulnerable

Physical Characteristics

Attribute	Coastal Silver-stiletto	River Thread-moss
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.

River Thread-moss

Habitat

Native to Europe, inhabiting ecosystems characteristic of the region.

Range

Distributed across Norway and Sweden. Currently classified as Vulnerable on the IUCN Red List, this species faces significant conservation challenges across its range.

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.