Cobweb spider vs common grey sea slug

Enoplognatha thoracica compared with Aeolidia papillosa

Key Differences

• Cobweb spider is Vulnerable while common grey sea slug is Least Concern.

Taxonomic Classification

Rank	Cobweb spider	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	Enoplognatha	Aeolidia
Species	Enoplognatha thoracica	Aeolidia papillosa

Evolutionary Relationship

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

Conservation Status

Cobweb spider

VU — Vulnerable

common grey sea slug

LC — Least Concern

Physical Characteristics

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

Habitat & Geographic Range

Cobweb spider

Habitat

Typically found in terrestrial habitats from forests to deserts.

Range

Found across Europe (4 countries) and North America (Canada, United States). Currently classified as Vulnerable on the IUCN Red List, this species faces significant conservation challenges across its range.

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 spider

Enoplognatha thoracica is a slender cobweb spider in the family Theridiidae, a widespread group of three-dimensional web-building spiders found across the temperate regions of Europe and North America. This small spider, typically measuring 3–5 millimeters in body length, constructs irregular, tangled cobwebs in low vegetation, hedgerows, meadow margins, and scrubby habitats where it captures small flying and crawling arthropods. The body is pale yellowish-brown to creamy white with darker markings on the abdomen, and the legs are long and slender relative to body size, adapted for navigating the three-dimensional structure of its web. Like other theridiids, Enoplognatha thoracica uses a gum-foot trap technique in which sticky vertical threads attached to the substrate at their lower ends snap insects upward when disturbed, immobilizing prey effectively. The species occupies a range spanning much of Europe eastward into temperate Asia and has established populations in parts of North America, likely through accidental human-mediated dispersal. Females produce egg sacs that are guarded within the web until hatching. The species is associated with disturbed and edge habitats and tolerates moderate agricultural landscapes. It is classified as Vulnerable by some assessments, reflecting localized population pressures from habitat loss and intensification of land use in parts of its range, though other evaluations consider it more broadly secure.

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 4 countries:

🇧🇪 Belgium 🇩🇰 Denmark 🇳🇴 Norway 🇸🇪 Sweden