Belly-shaped Hard Grass vs Chocolate arion

Aegilops ventricosa compared with Arion rufus

Key Differences

Belly-shaped Hard Grass is Least Concern while Chocolate arion is Vulnerable.

Taxonomic Classification

Rank	Belly-shaped Hard Grass	Chocolate arion
Kingdom	Plantae (Plants)	Animalia (Animals)
Phylum	Magnoliophyta (Flowering Plants)	Mollusca (Mollusks)
Class	Liliopsida (Monocots)	Gastropoda (Gastropoda)
Order	Poales (Grasses)	Stylommatophora (Stylommatophora)
Family	Poaceae (Grass Family)	Arionidae
Genus	Aegilops	Arion
Species	Aegilops ventricosa	Arion rufus

Conservation Status

Belly-shaped Hard Grass

LC — Least Concern

Chocolate arion

VU — Vulnerable

Physical Characteristics

Attribute	Belly-shaped Hard Grass	Chocolate arion
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Belly-shaped Hard Grass

Habitat

Typically found in grasslands, wetlands, forests, and cultivated landscapes.

Range

Distributed across Belgium, France, Netherlands, and United Kingdom.

Chocolate arion

Habitat

Inhabits temperate broadleaf and mixed forests and Mediterranean forests and woodlands within the Palearctic biogeographic realm. Populations are also found in montane and highland environments at higher elevations.

Range

Found across Europe (7 countries) and North America (United States). Currently classified as Vulnerable on the IUCN Red List, this species faces significant conservation challenges across its range.

Belly-shaped Hard Grass

The Belly-shaped Hard Grass (Aegilops ventricosa) is a species in the genus Aegilops. It is currently classified as Least Concern on the IUCN Red List. Typically found in grasslands, wetlands, forests, and cultivated landscapes.

Chocolate arion

The Chocolate Arion (Arion rufus), also known as the Large Red Slug or Chocolate Slug, is one of Europe's largest terrestrial slugs, with adults reaching up to 15 centimetres in length. It belongs to the family Arionidae within the phylum Mollusca, and despite its common name, adults display highly variable colouration ranging from reddish-orange to dark brown and nearly black — only certain colour morphs exhibit the chocolate-brown hue that partly inspired the name. Arion rufus is native to western and central Europe, where it inhabits woodland, hedgerows, gardens, agricultural land, and other moist habitats. It is also established as an introduced species in parts of North America. Like other arionid slugs, it is primarily a detritivore and herbivore, consuming dead plant material, fungi, living plant tissue, and sometimes carrion. It shelters under logs, stones, and leaf litter during dry or cold conditions, becoming active — particularly at night — during warm, moist weather. Chocolate arion can cause significant damage to gardens and crops. Reproduction is hermaphroditic; slugs exchange sperm and lay batches of translucent eggs in soil or under debris. The IUCN classifies this species as Vulnerable, reflecting pressures on native European populations from habitat change and, possibly, competition and hybridisation with related Arion species.