Brook Floater vs Coastal Silver-stiletto

Alasmidonta varicosa compared with Acrosathe annulata

Key Differences

• Brook Floater is Vulnerable while Coastal Silver-stiletto is Least Concern.

Taxonomic Classification

Rank	Brook Floater	Coastal Silver-stiletto
Kingdom same	Animalia (hayvan)	Animalia (hayvan)
Phylum	Mollusca (Yumuşakçalar)	Arthropoda (Eklem bacaklılar)
Class	Bivalvia (Midyeler)	Insecta (böcek)
Order	Unionida (Unionoida)	Diptera (Çift kanatlılar)
Family	Unionidae	Therevidae
Genus	Alasmidonta	Acrosathe
Species	Alasmidonta varicosa	Acrosathe annulata

Evolutionary Relationship

Brook Floater and Coastal Silver-stiletto share a common ancestor at the Kingdom level: Animalia. (hayvan)

Conservation Status

Brook Floater

VU — Vulnerable

Coastal Silver-stiletto

LC — Least Concern

Physical Characteristics

Attribute	Brook Floater	Coastal Silver-stiletto
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Brook Floater

Habitat

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

Range

Found in United States. Currently classified as Vulnerable on the IUCN Red List, this species faces significant conservation challenges across its range.

Coastal Silver-stiletto

Habitat

Typically found in virtually all terrestrial and freshwater habitats.

Range

Distributed across Belgium, Denmark, Norway, and Sweden.

Brook Floater

The Brook Floater (Alasmidonta varicosa) is a species in the genus Alasmidonta. It is currently classified as Vulnerable on the IUCN Red List. Native to North America, inhabiting ecosystems characteristic of the region.

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.