Girdled snail (Hygromia cinctella)

Synonyms: Helix cinctella, Hygromia (Hygromia) cinctella

Description:

Girdled snail (Hygromia cinctella) is a small land snail from the Mediterranean region that has spread widely through Europe and turned up at scattered sites in the United States [1][2]. It was first found in Michigan in 2004 [1]. MISIN tracks it because it gathers in large numbers in gardens and hedges and feeds on many plants, which could put pressure on native plant communities [1].

Identification:

The girdled snail is small, with a distinctive flattened pyramid- or top-shaped shell about 6?7 mm tall and 10?14 mm wide ? roughly the width of a fingernail ? coiled in five to six whorls with a raised cone on top and a flat underside [1]. Its standout feature is a sharp ridge (a keel) running around the widest part of the shell, edged with a pale white band that "girdles" the shell and gives the snail its name [1]. The rest of the shell is variable in color, from whitish gray to a horny brown, sometimes with darker flecks, and finely lined [1].

These snails like damp weather and human-made spots, so look for them in gardens, on hedges, along walls, and among ivy and weedy plants ? often gathered in numbers ? from spring through fall [1]. The white-banded keel is the quickest way to pick this snail out from the rounder common garden snails around it [1].

At-a-glance cues:

1. Small flattened pyramid-shaped shell about 10?14 mm wide (fingernail-sized), with 5?6 whorls [1]
2. Sharp keel (ridge) around the widest part of the shell, edged with a pale white band ? the "girdle" [1]
3. Shell color variable, whitish gray to horny brown, sometimes with dark flecks [1]
4. Gathers in numbers on hedges, walls, and garden plants in damp weather [1]

Habitat:

The girdled snail lives mostly around people. It is common in gardens, on hedges, along roadsides and stone walls, and among grass, nettles, ivy, and other leafy plants, where it can gather in large numbers [1][2]. It favors damp, sheltered, disturbed ground rather than deep wild habitat, which is part of why it travels so easily with garden and landscaping material [1][2].

The snail is native to the Mediterranean region [1][2]. From there it has spread quickly across much of Europe and has been introduced to the United States, where it was first recorded in Michigan in 2004 [1][2]. It is not a specialist ? it feeds on a wide range of living and dead plant material, which lets it survive in many garden and yard settings [1].

Reproduction:

The girdled snail spreads almost entirely by hitchhiking with people. The snails and their eggs travel in the soil of potted plants and nursery stock, in garden waste and mulch, and on landscaping materials moved from place to place [1][2]. Its strong link to gardens and hedges means it most often arrives on new plants or in moved soil rather than spreading far on its own [1][2].

Like most land snails, the girdled snail is a hermaphrodite ? each individual has both male and female parts ? and it lays eggs in soil or under cover such as leaf litter, stones, and pots [1]. Detailed egg counts and timing for North America are not well documented, but as a small garden snail it can build up quickly once established, especially in mild, damp conditions [1]. For control, the most reliable steps are to remove snails before they multiply and to inspect incoming plants and soil so new snails and eggs are not introduced (see Management) [1].

Impact and Damage:

The girdled snail is not known to harm people or pets, and it is not considered a major crop pest. Its main nuisance is in the garden: it can gather in large numbers on hedges, walls, and plantings, and it chews on a variety of garden plants [1]. For most homeowners it is a minor pest that is more noticeable for its numbers than for serious damage [1].

For natural areas, the concern is that a snail able to mass in large numbers and feed on many kinds of plants could compete with native snails and put added grazing pressure on native plant communities where it spreads [1]. So far its impacts in North America are not well documented, so it is best treated as a species to watch and to keep from spreading rather than one with proven large-scale harm [1].

Similar species:

A few other small snails of gardens and dry, grassy places can be mistaken for the girdled snail, though its white-banded keel sets it apart.

Carthusian snail (Monacha cartusiana) is a small pale introduced snail of similar habitats, but its shell is smoothly rounded with no keel, lacking the girdled snail's sharp white-edged ridge.

Eastern heath snail (Xerolenta obvia) is another small introduced grass snail, but it is chalky white with dark spiral bands and a wide-open navel, rather than the girdled snail's keeled, white-banded shell.

Brown garden snail (Cornu aspersum) shares gardens with the girdled snail, but it is far larger with a big, rounded, wrinkled brown shell and no keel.

Monitoring and rapid response:

Signs to watch for:

1. Small, flat-topped snails with a sharp keel and a pale white band around the widest part of the shell, on hedges, walls, and garden plants in damp weather [1]
2. Snails gathered in large numbers in gardens, along hedges, and among ivy or weedy plants [1]
3. Small keeled snails turning up after new nursery plants, soil, or mulch are brought in [1][2]

What you can do:

1. Hand-pick snails ? easiest when they cluster on stems, hedges, and walls in damp weather ? and drop them in soapy water or seal them in a bag for the trash [1].
2. Remove daytime shelter such as debris, leaf litter, stones, and pots, and thin dense ground cover near gardens and beds [1].
3. Inspect new potted plants, soil, and mulch for snails and their eggs before bringing them home, and don't move infested plants or garden material [1][2].
4. Natural area crews can survey gardens, hedgerows, and roadsides near known sites, focus first on small outlying populations to stop spread, and clean soil and snails off tools and boots between sites [1].
5. Report sightings (below) ? this snail is known from only a few US sites, so early reports are valuable [1].

When to call a professional:

1. Established or spreading populations, or damage to a nursery or planting ? contact your local cooperative extension office or state agriculture program for current guidance [1].
2. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Michigan Department of Natural Resources, Invasive Species Program. Girdled Snail (Hygromia cinctella). michigan.gov/invasives
2. University of Georgia, Center for Invasive Species and Ecosystem Health (Invasive.org / EDDMapS). Girdled Snail (Hygromia cinctella (Draparnaud, 1801)). invasive.org

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