Plants and Animals

Hendersonia occulta Cherrystone drop

species photo
Daria Hyde
species photo
Kraig Korroch
species photo
Kraig Korroch
species photo
Kraig Korroch

Key Characteristics

The cherystone drop is a small land snail (0.2-0.3 in/5-8 mm in diameter and height) with a reddish-brown helicoid shell (low, flattened spiral) with 4.5 to 6.5 whorls that curve to the right and regularly increase in diameter. The crescent-shaped opening can be sealed with an operculum (lid), and the shell has no umbillicus (central opening on the base).

Status and Rank

US Status:
State Status: T - Threatened (legally protected)
Global Rank: G4 - Apparently secure
State Rank: S1 - Critically imperiled

Occurrences

CountyNumber of OccurrencesYear Last Observed
Delta22014

Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.

Habitat

The species is found in cool, forested, calcareous slopes with a thick layer of humus above rivers and lakes.

Natural Community Types

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Management Recommendations

Land-use activities that remove forest canopy cover and alter critical habitat requirements such as cool microclimate and moisture availability should be avoided at occupied sites. These would include land-use activities such as timber harvesting, residential development, and road building. The species also is sensitive to excessive trampling and ORV use.

Active Period

Active from first week of April to fourth week of September

Survey Methods

Surveys can be conducted anytime during the growing season, but are most successful in spring and fall following rain showers or when the soil is moist, and during higher relative humidity conditions and cooler temperatures. Visual surveys consist of looking for individuals crawling on the ground, in moist leaf litter, and on or under woody debris. Litter sampling consists of collecting soil and leaf litter samples in the field and drying, sifting and looking for snail shells in the litter samples in the laboratory.

Visual survey

Survey Period: From first week of April to fourth week of June

Humidity: Humid
Precipitation: Just after rain

Litter sampling

Survey Period: From first week of April to fourth week of June

Humidity: Humid
Precipitation: Just after rain

Visual survey

Survey Period: From third week of August to fourth week of September

Humidity: Humid
Precipitation: Just after rain

Litter sampling

Survey Period: From third week of August to fourth week of September

Humidity: Humid
Precipitation: Just after rain

References

Survey References

  • Nekola, J.C. 1998. Terrestrial Gastropd Inventory of the Niagaran Escarpment and Keweenaw Volcanic Belt in Michigan's Upper Peninsula. Small Grants Program, 1998 Nongame Wildlife Fund, Natural Heritage Program, Michigan DNR, Lansing. 133pp.
  • Schilthuizen, M. and H.A. Rutjes. 2001. Land snail diversity in a square kilometer of tropical rainforest in Sabah, Malaysian Borneo. Journal of Molluscan Studies 67:417-423.

Technical References

  • Evers, D.C. 1994. Endangered and Threatened Wildlife of Michigan. The University of Michigan Press, Ann Arbor. 412pp.
  • Nekola, J.C. 1998. Terrestrial Gastropd Inventory of the Niagaran Escarpment and Keweenaw Volcanic Belt in Michigan's Upper Peninsula. Small Grants Program, 1998 Nongame Wildlife Fund, Natural Heritage Program, Michigan DNR, Lansing. 133pp.