| | The families of non-marine molluscs of Britain and Ireland (slugs, snails and mussels) |
Morphology. Slugs, with no external shell.
45–75 mm long when fully extended. With a small, totally internal, symmetrical shell. Not slender and worm-like when extended. Contracting protectively when molested, but not assuming the hemispherical or sub-globular form characteristic of Arionidae. The body variable in colour: black, brown or dark-, brownish- or yellowish-grey, sometimes speckled or reticulated with black. The mucous colourless, or milky. The mantle anterior and large; shagreened, and exhibiting a large dorsal island, demarcated by a conspicuous groove. The animal with two pairs of tentacles (the anterior pair short). Eyes at the tips of the posterior tentacles. The jaw not as in Zonitidae and Limacidae (?). The respiratory pore towards the posterior right of the mantle. The tail dorsally sharply keeled, the keel reaching to the mantle.
General biology, ecology. Terrestrial. Lifestyle rather subterranean (T. sowerbyi), or not subterranean. In woods and hedges, gardens and fields, M. gagates, T. budapestensis and T. sowerbyi being notable pests. Herbivorous.
Hermaphrodite.
Classification. Gastropoda; Pulmonata.
Representation in Britain and Ireland. Milax (1, “Jet slug”), Tandonia (3, “Keeled slug, Budapest slug”).
Illustrations. • Milax gagates and Tandonia sowerbyi: assorted varieties (Taylor). MILACIDAE. 9–14, Milax gagates (Draparnaud), "Jet Slug", animals 45–55 mm. long when extended. 15–20, Tandonia sowerbyi (Férussac), "Sowerby's Keeled slug", 60–75 mm. From Taylor (1906). • Milax gagates and Tandonia sowerbyi, with other slugs (Ellis). MILACIDAE. 1, Milax gagates (Draparnaud), "Jet Slug", extending to 45–55 mm.; 2, Tandonia sowerbyi (Férussac), "Sowerby's Keeled Slug", 60–75 mm. ARIONIDAE. 3, Geomalacus maculosus Allman, "Kerry Slug", extending to 60–90 mm. 4, Arion subfuscus Draparnaud, "Dusky Slug", 50–70 mm.; 5, Arion circumscriptus agg., "Bourguignat's Slug", 30–40 mm.; 6, Arion ater (Linn.) var. livida, "Large Black Slug", 60–130 mm.; 7 and 8, Arion intermedius Normand, "Hedgehog Slug", extending to 15–20 mm.; 9, Arion hortensis agg., "Garden Slug", 25–35 mm. TESTACELLIDAE. 10, Testacella haliotidea Draparnaud, "Shelled Slug", 70–100 mm. From Ellis (1926). • Milax gagates and Tandonia sowerbyi (Reeve). MILACIDAE. 1, Tandonia sowerbyi (Férussac), "Sowerby's Keeled slug". 2, Milax gagates (Draparnaud), "Jet slug". From Reeve (1863, with approximate 2cm scale added). • Tandonia sowerbyi, with Arionidae, Agriolimacidae and Limacidae (Adams). ARIONIDAE. 1, Arion ater (Linn.), "Large Black Slug"; 2, Arion intermedius Normand, "Hedgehog Slug"; 3, Arion hortensis agg., "Garden Slug"; 5, Geomaculus maculosus Allman, "Kerry Slug". LIMACIDAE. 6, Limax maximus Linn., "Great Grey Slug"; 7, Limax flavus Linn., "Yellow Slug"; 8, Lehmannia marginata (Müller), "Tree Slug". AGRIOLIMACIDAE: 4, Deroceras laeve (Müller), "Marsh Slug"; 9, Deroceras reticulatum (Müller), "Field or Milky Slug". MILACIDAE: 10, probably Tandonia sowerbyi (Férussac), "Sowerby's Keeled Slug". From Adams (1896).
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2005 onwards. The families of non-marine molluscs of Britain and Ireland (slugs, snails and mussels). Version: 5th August 2019. delta-intkey.com’.
