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Glass Snails

Vitrinidae Fitzinger, 1833

 

Contents

Introduction

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Ear Shaped Glass Snail (Eucobresia diaphana).
Photo: © Stefan Haller (schneckenfoto.ch).
   
 
Mantle flap of Eucobresia diaphana.
Photo: Andreas Heidl. 

Mountain Glass Snail (Hessemilimax kotulae). Photo: Gianbattista Nardi.		  
The name "glass snails" was coined because of the glass-like transparent and fragile shell carried by these small snails, which generally only grow to a body size of less than 20 mm. Several species of glass snails native to Central Europe typically live on the ground in sufficiently moist habitats, beneath decaying leaf litter and moss, along spring margins and stream banks, and even at high elevations in mountainous regions. Glass snails usually emerge at the surface only in autumn, with the arrival of cool and damp weather, where they remain throughout the winter and can even be found beneath melting snow. Since glass snails are remarkably tolerant of cold conditions, they occur far into the north beyond the Arctic Circle. In mountainous regions, some species are capable of living at elevations exceeding 3,000 m above sea level.

The extremely thin shell of glass snails already reveals their close similarity to slugs. For example, when comparing the Translucent Glass Snail (Vitrina pellucida) with the Ear-Shaped Glass Snail Eucobresia diaphana, it becomes obvious that while the Crystal Snail still owns a shell into which it can completely withdraw, Eucobresia diaphana has a comparatively smaller shell with fewer whorls, the final whorl being expanded into an ear-like shape, which also explains its common name. As a consequence, it can no longer fully retract into its shell.

Differences can also be seen in the shape of the mantle. From the Translucent Glass Snail to other species of glass snails, one can observe that the mantle shield increasingly extends over the shell from the front. In addition, a mantle lobe of varying size extends over the spire on the right side. In some species of glass snails, the shell may become almost completely covered by the mantle.

For example, Oligolimax annularis carries a relatively large shell into which it can still fully withdraw. Its genus name Oligolimax literally means "less slug-like", because among glass snails it shows the fewest slug-like characteristics. On the other end, the Half-Slug Glass Snail (Semilimax semilimax) has a shell that is already so extensively overgrown by the mantle that, as its name Semilimax ("half slug") suggests, it has become almost slug-like (see illustrations at the bottom of the page).


Madeirovitrina ruivensis: Madeira, Portugal.
Photo: Sébastien Sant (iNaturalist).		  
This evolutionary trend can be observed particularly well in the subfamily Plutoniinae on the island of Madeira. For example, Madeirovitrina marcida still resembles Vitrina pellucida externally, carrying a well-developed coiled shell. In Madeirovitrina albipalliata, however, the shell is already largely overgrown by the mantle; in Madeirovitrina nitida this development is even more pronounced, and finally in Madeirovitrina ruivensis and Madeirovitrina behnii, the shell can no longer be seen externally at all. Externally, the animal appears to be essentially a slug.

Similar situations can be observed in other groups of snails, for example in the tropical family Helicarionidae. Slugs have evolved repeatedly and independently during the evolutionary history of land snails. This evolutionary pathway of shell reduction is known as vitrinisation, named after the family Vitrinidae, the glass snails, which represent only one of several possible evolutionary routes towards this strategy.


 		 Groh, K.; Rähle, W.; Kittel, K.; Hemmen, J.; Bank, R. (2009): Corrections and Additions to Mary B. Seddon's "The Landsnails of Madeira". Conchylia 40, (3/4), 2 - 25. (In the paper, Madeirovitrina is still referred to as Plutonia).

 		 MolluscaBase eds. (2025): Madeirovitrina Groh & Hemmen, 1986.

Similar Conditions canbe observed in other snail groups, such as the tropical family Helicarionidae. Slugs have evolved independently during the evolution of terrestrial snails. The evolutionary path of shell reduction is also referred to as vitrinisation, after the family of glass snails (Vitrinidae), which have gone but only one of the paths possible in this strategy.

More about Slugs.
Image Display: Glass Snail Relatives (Vitrinoidea: Systematics outdated).
Vitrinisation: The reduction of the snail shell in terrestrial gastropods.

Systematics

Order: Stylommatophora
Superfamily: Limacoidea
Family: Vitrinidae Fitzinger 1833

Source: MolluscaBase eds. (2021): Vitrinidae Fitzinger, 1833.

Systematically the glass snail family (Vitrinidae) is placed in the superfamily of Limacoidea, which means they are most closely related to keel-back slugs (Limacidae).

Translucent Glass Snail - Vitrina pellucida (O. F. Müller, 1774)

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Translucent Glass Snail (Vitrina pellucida): Helperknapp,
Luxemburg. Photo: Christiane Wolff (iNaturalist).		  
Description: The Translucent Glass Snail has a glossy and smooth shell, the last whorl of which is not wider than half of the overall shell width, looking at the shell tip. The shell whorls are rounded, and the snail can withdraw into its shell completely. The mantle shield is narrow, and the black mantle flap does not cover the shell tip.

Size: L: 4 - 6 mm; W: 2,5 - 3,5 mm; Length of animal: 10 mm.

Habitat and Distribution: The Translucent Glass Snail generally inhabits moderately open meadow locations, humid or dry habitats in deciduous and coniferous forests, in grassland or in fallow land. Of all glass snails, this species lives in the driest habitats, but is very adaptable to larger ecological differences.Vitrina pellucida can also be found on rocks and walls, in the pebble layer of streams, in the waterside vegetation and even on alpine meadows. Sometimes it is present in places with little vegetation cover, and it even tolerates soil of a more acidic composition.

The distribution area of this species spreads from Europe as far as Central Asia, in the North even beyond the Arctic Circle. In Switzerland, Vitrina pellucida occurs in elevations up to 2700 m above MSL.

Francisco Welter-Schultes: Vitrina pellucida species homepage.
MolluscaBase eds. (2025): Vitrina pellucida (O. F. Müller, 1774).
Naturportal Südwest (German): Vitrina pellucida.

Ear Shaped Glass Snail - Eucobresia diaphana (Draparnaud, 1805)

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Ear Shaped Glass Snail (Eucobresia diaphana).
Photo: © Stefan Haller (schneckenfoto.ch).
Description: Contrary to its relative described before, the Ear Shaped Glass Snail has a flat shell with fine white stripes, which, however, possesses more than two whorls. The last whorl is strongly extended and ear shaped. The shell spindle (columella) is bent, so that the previous whorls can be seen. The animal itself is of a dark colour, in higher elevations in the mountains it can also be light gray; the snail cannot withdraw into its shell. The mantle flap completely covers the shell tip (apex). Anatomical characters tell the species apart from Eucobresia pegorarii.


Ear Shaped Glass Snail (Eucobresia diaphana): Štěchovice,
Czechia. Photo: Michal Honskus (iNaturalist).		  
Size: L: 6 - 6,5 mm; W: 3,3 mm; Length of animal: 16 - 18 mm.

Habitat and Distribution: The Ear-Shaped Glass Snail lives in humid and cool places on the valley floor and in the mountains. In the low country, Eucobresia diaphana is found in shadowy and humid habitats in forests, in higher elevations also in open places, between short bushes and in grassland with a sufficient number of hiding places.

Eucobresia diaphana is found in Europe, from the Pyrenees as far east as the Balkans and as far north as Northern Germany, the southeastern Netherlands and especially in the Alps. In Switzerland, it is found as far up as 2900 m above MSL.

Threat Situation: In Rhineland-Palatia, Eucobresia diaphana is rated as endangered (see: IUCN Threat Categories).

Francisco Welter-Schultes: Eucobresia diaphana species homepage.
MolluscaBase eds. (2025): Eucobresia diaphana (Draparnaud, 1805).
Naturportal Südwest (German): Eucobresia diaphana.

Mountain Glass Snail - Hessemilimax kotulae (Westerlund, 1883)

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Mountain Glass Snail (Hessemilimax kotulae): Krhanice, Cze-
chia. Photo: Michal Honskus (iNaturalist).		  
Description: The shell of Hessemilimax kotulae is characterized by an especially wide final whorl. The shell wall extends to the outside, so the inner whorls become visible. The singular whorls are flat, and the shell surface is smoother and glossier than in other glass snails, such as Semilimax. According to Ehrmann (1956), the Mountain Glass Snail is "the species furthest advanced on the way to becoming a slug" (p. 103).

Size: L: 4 - 6 mm; W: 3 - 4,5 mm; Length of animal: 12 - 15 mm.

 
Mountain Glass Snail (Hessemilimax kotulae).
Photo: Gianbattista Nardi.
Habitat and Distribution: Like its name says, the Mountain Glass Snail lives only in the mountains. It is predominantly found in forests, where its habitat is in cool and shadowy places in humid moss, under stones and in the ground litter. Only rarely it is found beyond the tree border in the mountains, but then it is found in humid and mossy dwarf bushes, as well as on alpine meadows beneath stones.

Hessemilimax kotulae is widely spread in the Alps and in the Carpathians, in Switzerland the species is found only between 1300 und 2600 m above MSL.

Threat Situation: The Mountain Glass Snail is rare and dispersed. In Bavaria it is rated as critically endangered and in Austria as endangered (see: IUCN Threat Categories).

Francisco Welter-Schultes: Semilimax kotulae species homepage.
MolluscaBase eds. (2025): Hessemilimax kotulae (Westerlund, 1883).
Naturportal Südwest (German): Hessemilimax kotulae.
Nardi, G.; Niero, I.; Braccia, A. (2007): Nota sui Vitrinidae (Gastropoda, Pulmonata) viventi in provincia di Brescia. Natura Bresciana 35 (2007), 101 - 119.

Complete Species List for Austria

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Source: MolluscaBase eds. (2021): Vitrinidae Fitzinger, 1833.

Vitrinidae Fitzinger, 1833

 
Oligolimax annullaris: Kütahya kalesi, Turkey.
Photo: Mehmet Akif Suna (iNaturalist) 
   
 
Wide-mouthed Glass Snail (Semilimax semilimax): Moszczan-
ka, Poland. Photo: Michał Górski (iNaturalist).
   
 
Short Glass Snail (Vitrinobrachium breve):  Ballenstedt, Harz,
Germany. Photo: Amigolimax (iNaturalist). 

Vitrininae Fitzinger, 1833

Eucobresia H.B. Baker, 1929

Eucobresia diaphana (Draparnaud, 1805)
Eucobresia nivalis (Dumont & Mortillet, 1854)
Eucobresia pegorarii (Pollonera, 1884)
Eucobresia glacialis (Forbes, 1837)

Hessemilimax Schileyko, 1986

Hessemilimax kotulae (Westerlund, 1883)

Oligolimax P. Fischer, 1878

Oligolimax annularis (S. Studer, 1820)

Semilimax Stabile, 1859

Semilimax semilimax (J. Férussac, 1802)
Semilimax carinthiacus (Westerlund, 1886)

Semilimacella Soós, 1917

Semilimacella carniolica (O. Boettger, 1884)

Vitrinobrachium Künkel, 1929

Vitrinobrachium breve (A. Férussac, 1821)

Vitrina Draparnaud, 1801

Vitrina pellucida (O. F. Müller, 1774)

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Literature

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With Photos by Stefan Haller:
http://www.schneckenfoto.ch.

Latest Change: 27.05.2026 (Robert Nordsieck).
Latest Link Check: 27.05.2026.