Coastal Silver-stiletto vs

Acrosathe annulata compared with Cocconeis disculus

Key Differences

Coastal Silver-stiletto is Least Concern while is Not Evaluated.

Taxonomic Classification

Rank	Coastal Silver-stiletto
Kingdom	Animalia (Animals)	Chromista (Chromista)
Phylum	Arthropoda (Arthropods)	Ochrophyta (Ochrophyta)
Class	Insecta (Insects)	Bacillariophyceae (Bacillariophyceae)
Order	Diptera (Diptera)	Achnanthales (Achnanthales)
Family	Therevidae	Cocconeidaceae
Genus	Acrosathe	Cocconeis
Species	Acrosathe annulata	Cocconeis disculus

Conservation Status

Coastal Silver-stiletto

LC — Least Concern

NE — Not Evaluated

Physical Characteristics

Attribute	Coastal Silver-stiletto
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.

Habitat

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

Range

Distributed across Brazil, Norway, and Sweden.

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.

Cocconeis disculus is a freshwater and brackish-water diatom in the family Cocconeidaceae, belonging to the class Bacillariophyceae—the diatoms, a group of unicellular photosynthetic algae encased in ornate silica cell walls called frustules. Like all members of the genus Cocconeis, C. disculus is an adnate, epiphytic species, meaning it lives attached to substrates—typically the surfaces of aquatic macrophytes, filamentous algae, and sediment particles—rather than living freely in the water column. The frustule of Cocconeis species is distinctive in its bilateral symmetry and the characteristic difference between its two valves: the rapheless valve (RV) lacks the raphe slit present on the raphe valve (RV), a feature used in species identification. Cocconeis disculus has been documented from freshwater bodies across South America and various parts of the Northern Hemisphere, with distribution reflecting its tolerance of a range of water temperatures and nutrient conditions. Diatoms like C. disculus are foundational components of aquatic food webs, fixing carbon through photosynthesis and providing a nutritious food source for grazing invertebrates, protists, and larval fish. The species also contributes to the biosilica cycle through the production and dissolution of its silica frustule. As a benthic, substrate-attached organism, Cocconeis disculus serves as a sensitive bioindicator of water quality conditions in freshwater monitoring programs. Its conservation status is not formally evaluated.