Cobweb weaver vs common grey sea slug

Steatoda nobilis compared with Aeolidia papillosa

Key Differences

• Cobweb weaver is Not Evaluated while common grey sea slug is Least Concern.

Taxonomic Classification

Rank	Cobweb weaver	common grey sea slug
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum	Arthropoda (Arthropods)	Mollusca (Mollusks)
Class	Arachnida (Arachnids)	Gastropoda (Gastropoda)
Order	Araneae (Araneae)	Nudibranchia (Nudibranchia)
Family	Theridiidae	Aeolidiidae
Genus	Steatoda	Aeolidia
Species	Steatoda nobilis	Aeolidia papillosa

Evolutionary Relationship

Cobweb weaver and common grey sea slug share a common ancestor at the Kingdom level: Animalia. (Animals)

Conservation Status

Cobweb weaver

NE — Not Evaluated

common grey sea slug

LC — Least Concern

Physical Characteristics

Attribute	Cobweb weaver	common grey sea slug
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic 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).

common grey sea slug

Habitat

Typically found in terrestrial and aquatic habitats including forests and freshwater.

Range

Distributed across Belgium, Chile, Denmark, Norway, and Sweden.

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.

common grey sea slug

<em>Aeolidia papillosa</em>, commonly known as the common grey sea slug, is a nudibranch mollusc belonging to the genus Aeolidia within the family Aeolidiidae. Despite the species name referencing terrestrial and aquatic habitats including forests and freshwater, <em>Aeolidia papillosa</em> is primarily a marine organism. Its range includes Belgium, Chile, Denmark, Norway, and Sweden, indicating a distribution across the North Atlantic and into South American waters. Common grey sea slug is assessed as Least Concern on the IUCN Red List. The species is typically found in intertidal and subtidal zones, where it preys on sea anemones and stores stinging cells from its prey in its dorsal cerata for defense. Biological traits of this species remain poorly documented in the scientific literature.

Shared Countries

Both species can be found in 2 countries:

🇧🇪 Belgium 🇩🇰 Denmark