Andersson's arctic moss vs Cobweb weaver

Arctoa anderssonii compared with Steatoda nobilis

Key Differences

Andersson's arctic moss is Endangered while Cobweb weaver is Not Evaluated.

Taxonomic Classification

Rank	Andersson's arctic moss	Cobweb weaver
Kingdom	Plantae (Plants)	Animalia (Animals)
Phylum	Bryophyta	Arthropoda (Arthropods)
Class	Bryopsida (Bryopsida)	Arachnida (Arachnids)
Order	Dicranales (Dicranales)	Araneae (Araneae)
Family	Rhabdoweisiaceae	Theridiidae
Genus	Arctoa	Steatoda
Species	Arctoa anderssonii	Steatoda nobilis

Conservation Status

Andersson's arctic moss

EN — Endangered

Cobweb weaver

NE — Not Evaluated

Physical Characteristics

Attribute	Andersson's arctic moss	Cobweb weaver
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Andersson's arctic moss

Habitat

Native to Europe, inhabiting ecosystems characteristic of the region.

Range

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

Cobweb weaver

Habitat

Typically found in terrestrial habitats from forests to deserts.

Range

Widely distributed across Europe (7 countries), North America (United States), and South America (Ecuador).

Andersson's arctic moss

The Andersson's arctic moss (Arctoa anderssonii) is a species in the genus Arctoa. It is currently classified as Endangered on the IUCN Red List. Native to Europe, inhabiting ecosystems characteristic of the region.

Cobweb weaver

The noble false widow (Steatoda nobilis) is a theridiid spider that has attracted considerable media attention in the British Isles and along the Atlantic coast of Europe due to its painful but rarely dangerous bite and its rapid range expansion facilitated by human activity. Originally native to the Canary Islands and Madeira, the species arrived in southern England during the 19th century, likely via banana shipments, and has since spread northward through Britain and westward into Ireland, while also establishing populations along the Iberian Peninsula and Atlantic France. Females are robust, with a dark brown carapace and a distinctive cream-colored pattern on the bulbous abdomen that varies between individuals; females reach 8.5–14 millimeters in body length, making this one of the larger European theridiids. The species constructs persistent, tangled cobwebs in sheltered locations outside buildings—under window ledges, in door frames, and in garden walls—as well as within homes in cooler seasons. It is a generalist predator, capturing insects and other invertebrates, and has been reported to occasionally subdue prey considerably larger than itself, including small lizards. Steatoda nobilis venom produces steatodism, which can cause localized pain, swelling, and in rare cases systemic symptoms. Its conservation status has not been formally assessed, but its expanding range demonstrates considerable resilience.