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Montana Field Guides

Quick Gloss - Zonitoides arboreus
Other Names:  Helix arboreus, Zonites arboreus, Hyalina arborea, Helix breweri, Hyalina breweri, Helix whitneyi, Hyalina whitneyi

Native Species

Global Rank: G5
State Rank: S5

Agency Status


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General Description
A small shell, to 5.6 mm diameter and 3 mm in height, flattened heliciform, with weak incremental wrinkles and extremely small spiral striae (requiring strong magnification to see), about 4 to 4 1/2 whorls, the last not greatly expanded. Shell coloration is translucent olive to brown, glossy. Aperture is crescent-shaped, wider than high, lacking teeth (denticles); umbilicus relatively narrow, about 1/4 to 1/5 the shell diameter. Animal is bluish gray on the head, paler on the sides and foot, tentacles darker; lacks the orange mantle spot (visible through the shell) of Zonitoides nitidus (Hendricks 2012, Burke 2013). Internal anatomy is described by Pilsbury (1946).

Diagnostic Characteristics
A combination of small size (to about 6 mm diameter), whorls of much the same size (the last not greatly expanding), brownish color, relatively flat spire, relatively narrow umbilicus 1/4 or less the shell diameter), and shell generally smooth or wrinkled (not with striae or riblets), distinguishes Zonitoides from other shells. Z. arboreus differs from Z. nitidus by being smaller (to 5.6 mm diameter), having a nearly flattened spire, the shell translucent olive to brown, the mantle of the live animal lacking a dull orange spot visible through the shell.

Species Range
Montana Range Range Descriptions


Range Comments
North and Central America to the West Indies. Introduced to South America, Europe, and Asia. In Montana, reported from both sides of the Continental Divide in 28 counties. Elevation range is 655 to 2309 m (2150 to 7575 ft). It may be relatively abundant in some locations; 42 were found at a site in Chouteau County in late September (Hendricks 2012).

Observations in Montana Natural Heritage Program Database
Number of Observations: 337

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

A variety of forested habitats where moisture retained or available. Canopy species include most conifers (including junipers), cottonwoods, aspen, birches, green ash and American elm; secondary canopy includes alder, willow, dogwood, mountain maple, current and hawthorn. Often found under woody debris and rocks, in downed rotten wood, leaf litter, and duff. Inhabits isolated aspen stands (Hendricks 2012).

The species is a regular victim of larval snail-killing flies (Diptera: Sciomyzidae)(Foote 2007).

  • Literature Cited AboveLegend:   View Online Publication
    • Burke, T. E. 2013. Land snails and slugs of the Pacific Northwest. Corvallis, OR: Oregon State University Press. 344 p.
    • Foote, B.A. 2007. Biology of Pherbellia inflexa (Diptera: Sciomyzidae), a predator of land snails belonging to the genus Zonitoides (Gastropoda: Zonitidae). Entomological News 118:193-198.
    • Hendricks, P. 2012. A Guide to the Land Snails and Slugs of Montana. A report to the U.S. Forest Service - Region 1. Montana Natural Heritage Program, Helena, MT. vii + 187 pp. plus appendices.
    • Pilsbry, H.A. 1946. Land Mollusca of North America (north of Mexico), Volume II Part 1. Academy of Natural Sciences of Philadelphia Monograph Number 3 (2):1-520.
  • Additional ReferencesLegend:   View Online Publication
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    • Berry, S.S. 1913. A list of Mollusca from the Mussellshell Valley, Montana. Nautilus 26:130-131.
    • Berry, S.S. 1916. Notes of Mollusca of central Montana. Nautilus 29:124-128.
    • Berry, S.S. 1919. Mollusca of Glacier National Park, Montana. Proceedings of the Academy of Natural Sciences of Philadelphia 71:195-205.
    • Elrod, M.J. 1902. Daphnia pond, a study in environment. University of Montana Bulletin #16, Biological Series 5: 230-233.
    • Forsyth, R.G. 2004. Land snails of British Columbia. Royal British Columbia Museum: Victoria, British Columbia, Canada. 188 pp.
    • Frest, T.J. and E.J. Johannes. 2001. An annotated checklist of Idaho land and freshwater mollusks. Journal of the Idaho Academy of Science 36(2):1-51.
    • Maxell, B.A. 2016. Northern Goshawk surveys on the Beartooth, Ashland, and Sioux Districts of the Custer-Gallatin National Forest: 2012-2014. Montana Natural Heritage Program. Helena, MT. 114pp.
    • Russell, R.H. and R.B. Brunson. 1967. A check-list of molluscs of Glacier National Park, Montana. Sterkiana 26:1-5.
    • Squyer, H. 1894. List of shells from the vicinity of Mingusville, Montana. The Nautilus 8:63-65.
    • Vanatta, E.G. 1914. Montana shells. Proceedings of the Academy of Natural Sciences of Philadelphia 66:367-371.
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Quick Gloss — Zonitoides arboreus.  Montana Field Guide.  .  Retrieved on , from