Coastal Silver-stiletto vs Common Moonwort

Acrosathe annulata compared with Botrychium lunaria

Key Differences

Coastal Silver-stiletto is Least Concern while Common Moonwort is Endangered.

Taxonomic Classification

Rank	Coastal Silver-stiletto	Common Moonwort
Kingdom	Animalia (Animals)	Plantae (Plants)
Phylum	Arthropoda (Arthropods)	Tracheophyta
Class	Insecta (Insects)	Polypodiopsida (Polypodiopsida)
Order	Diptera (Diptera)	Ophioglossales (Ophioglossales)
Family	Therevidae	Ophioglossaceae
Genus	Acrosathe	Botrychium
Species	Acrosathe annulata	Botrychium lunaria

Conservation Status

Coastal Silver-stiletto

LC — Least Concern

Common Moonwort

EN — Endangered

Physical Characteristics

Attribute	Coastal Silver-stiletto	Common Moonwort
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 Moonwort

Habitat

Typically found in moist, shaded forest floors and tropical canopies.

Range

Widely distributed across Asia (Taiwan), Europe (5 countries), and North America (United States). Currently classified as Endangered 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.

Common Moonwort

Common Moonwort (<em>Botrychium lunaria</em>) is a small fern in the genus <em>Botrychium</em>, family Ophioglossaceae. It is distributed across Asia, Europe, and North America, with confirmed presence in Belgium, Denmark, Norway, Portugal, and Sweden, as well as Taiwan and the United States. The species is typically found in moist, shaded forest floors and tropical canopies. Common Moonwort is currently classified as Endangered on the IUCN Red List, indicating that it faces significant conservation challenges across its range. Its distinctive frond is divided into two parts: a sterile fan-shaped leaf portion with rounded lobes resembling a crescent moon, and a fertile spike bearing spore-bearing structures. As a fern ally rather than a flowering plant, it reproduces via spores rather than seeds. The species is associated with stable, undisturbed habitats including ancient grasslands, upland heaths, and rocky slopes. Its sensitivity to habitat disturbance and changes in land management are thought to contribute to population declines. Specific biological measurements such as lifespan and dimensions are not documented in available records.