Mesodon clausus
Yellow globelet

Key Characteristics

The yellow globelet (Mesodon clausus, also called Helix clausus and Polygyra clausus) is a land snail with a finely ribbed yellow to yellowish-brown shell of about .5 inches in diameter. Additional features of the shell include 4-5 whorls, a relatively high, dome-shaped spire, and a smooth, round aperature lacking a parietal tooth. The granulated body is a brown to black with a lighter underside, with short tentacles and long tapering eye pedunlces.

Status and Rank

  • State Status: SC
  • State Rank: SNR
  • Global Rank: G5


County NameNumber of OccurrencesYear Last Observed
Distribution map for Mesodon clausus

Updated 5/15/2018. 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.


The yellow globelet has been found in forested river valleys, grasslands, shrubby successional habitats and railroad embankments (Baker 1939).

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.


Identification and conservation of important habitat areas is an important first step toward land snail species management. Destruction of habitat through agricultural and residential development, as well as human disturbance, is considered the greatest threat to land snails, as they are incapable of widespread dispersal following such changes (Kay 1995). Moist microhabitats with uncompacted soil and a rich layer of organic litter are required by many species (Nekola 2003), including the yellow globelet. The loss of vegetative ground cover through mowing, intensive recreational use and heavy grazing may negatively affect this species. Wild and prescribed fire has a significant negative effect on land snail abundance and diversity (Applegarth 1999, Nekola 2002). Snag retention should be planned for, as large downed logs may provide important refuges during fire and drought (Applegarth 1999). Snails rapidly absorb and bioaccumulate chemical pollutants and heavy metals (Berger and Dallinger 1993, Regoli et al. 2006), and high exposure to heavy metals has been found to prevent reproduction (Notten et al. 2006). Herbicides and insecticides should be applied with caution and affected populations monitored to evaluate impacts.

Active Period

Breeding from first week of May to fourth week of June

Survey Methods

As visual detection of this species is difficult, specimens are collected by litter sampling in suitable habitat. Samples are thoroughly heat-dried, soaked in water for a number of hours to separate the various components, and finally passed through a series of sieves. The shells are then able to be hand-picked from the remaining sample material (Nekola 2003).

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at [Accessed Sep 22, 2018]


Survey References

Technical References

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