Cluster Spiderhead vs Coastal Silver-stiletto

Serruria glomerata compared with Acrosathe annulata

Taxonomic Classification

Rank	Cluster Spiderhead	Coastal Silver-stiletto
Kingdom	Plantae (Plants)	Animalia (Animals)
Phylum	Magnoliophyta (Flowering Plants)	Arthropoda (Arthropods)
Class	Magnoliopsida (Dicots)	Insecta (Insects)
Order	Proteales (Proteales)	Diptera (Diptera)
Family	Proteaceae	Therevidae
Genus	Serruria	Acrosathe
Species	Serruria glomerata	Acrosathe annulata

Conservation Status

Cluster Spiderhead

LC — Least Concern

Coastal Silver-stiletto

LC — Least Concern

Physical Characteristics

Attribute	Cluster Spiderhead	Coastal Silver-stiletto
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Cluster Spiderhead

Habitat

Typically found in diverse terrestrial habitats from tropical forests to temperate regions.

Coastal Silver-stiletto

Habitat

Typically found in virtually all terrestrial and freshwater habitats.

Range

Distributed across Belgium, Denmark, Norway, and Sweden.

Cluster Spiderhead

Serruria glomerata, the cluster spiderhead, is a flowering shrub endemic to the Cape Floristic Region of South Africa, one of the world's six recognized floral kingdoms and a global biodiversity hotspot. The species belongs to the family Proteaceae and is restricted to fynbos, the fire-adapted shrubland of the Western Cape characterized by nutrient-poor, often acidic soils of sandstone or granite origin. Like other Serruria species, S. glomerata produces intricate, lace-like flower heads composed of many small flowers surrounded by feathery, spider-like bracts, which are pollinated by a range of insects including bees and beetles. Serruria glomerata is assessed as Least Concern by the IUCN, though like all Cape fynbos plants it exists within a biodiversity-rich but geographically confined region under persistent pressure from agricultural expansion, urban development, invasive alien plants, and altered fire regimes. The genus Serruria comprises around 55 species, most endemic to the Western Cape. Many require fire for seed release and germination, and some have obligate relationships with specific ant species that cache and bury their seeds, a process called myrmecochory that aids in seed dispersal and protection from fire.

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.