Very remarkable is their great variety ofsizes and shapes. Snail shells can be coni-cal in form to very flat and disc-shaped.The shell of the largest species measuresmore than an inch in width, while the tini-est is less than 1/16th inch across.

The toothed globe snail (also top of

page) is widely distributed in Illinois

and common in hardwood forests.

Silently and slowly gliding inthe damp, hidden nooks aresome lowly yet importantmembers of Illinois’ naturalhabitats: the land snails.

Land snails, whichinclude slugs, are one of the

most understudied groups of animals,but they are certainly deserving of ourattention. Often bearing the reputationas mere pests, Illinois’native land snails playan essential role in thefunctioning of itsecosystems. Approxi-mately 124 species arecurrently known toinhabit the state’sforests and grasslands,with more than 70 per-cent of species occupy-ing wooded habitats insouthern Illinois.

Can snails live outside their shell? Can they bite? Test yourknowledge of these under-appreciated slime producers.

Land Snailsin Illinois

Story and PhotosBy Marla Coppolino

Named for the toothlike structure on

the shell, the bladetooth wedge is one of

the most common land snails in Illinois.

Xolotrema fosteribladetooth wedge, shell width 5/8 inchXolotrema fosteribladetooth wedge, shell width 5/8 inch

Mesodon zaletustoothed globe, shell width 1 inch

Mesodon zaletustoothed globe, shell width 1 inch

8 / OutdoorIllinois June 2009

Also notable is that the majority ofIllinois’ species are quite small—lessthan 1/4 inch in shell width—and mostof these inhabit the leaf litter of forest-ed areas. They might be hard to detectby the unaided (and unknowing)human eye, but they exist, and aredoing their jobs very well.Land snails and slugs are members of

the class Gastropoda, meaning “stom-ach-foot,” because they move upon alarge, muscular ventral surface called afoot. The animal’s internal organs,which include a digestive gland, lung,heart and reproductive organs, arelocated within the mantle cavity, insidethe shell of the animal. In the case ofslugs, the organs are just behind thehead region.Gastropods include both land and

aquatic snails, and are members of thephylum Mollusca, a diverse array of

invertebrate animals including clams,mussels, limpets, chitons, tusk shells,octopuses and squid. Land snails are spe-cial in that they evolved from aquaticancestors and possess many unique adap-tations to survive in terrestrial habitats.

The ShellSnails are easily recognizable animals

because of their distinctive shells. Likethose of their aquatic relatives, the landsnails’ shells offer protection frompredators for the soft-bodied animal.

But for land snails, the shell also offersprotection from desiccation, the mostserious threat to terrestrial existence.The snail can withdraw its body far intothe shell, and remain inactive for longperiods of time when it is hot and dryor in freezing temperatures.One common misconception about

land snails is that they can “crawl away”from their shells. This is not possiblebecause the snail is attached to its shelland it would survive for only a shorttime if removed. Only when a snail diesdoes it leave behind an empty shell.

The shell is present from the timethe snail develops as an embryo. As ahatchling, it is thin and flexible, and hasonly about one whorl (a 360 degree coilfrom the center). As snails eat and grow,the shell thickens and additional coilsform around the central axis. In adultsof some species, projections grow with-in the aperture (the opening of theshell), which, when withdrawn into itsshell, help protect the snail from preda-tors. The projections are thought tohelp stabilize the weight of the shellwhen the snail is actively moving about.Slugs are snails, too, but have

evolved to not require the full shell of

Previously believed to be extinct, the

only place in the world that the carinate

pillsnail (above) is known to exist is

some limestone bluffs in southern

Illinois. Found in moist woodlands, the

brittle button (right) has a blue-tinged

body and translucent shell.

The vivid, rust-color marking on the

tigersnail make it easy to identify this

common snail.Anguispira alternatatigersnail, shell width 7/8 inchAnguispira alternatatigersnail, shell width 7/8 inch

Euchemotrema hubrichticarinate pillsnail, shell width 3/8 inchEuchemotrema hubrichti

carinate pillsnail, shell width 3/8 inch

Mesomphix friablisbrittle button, shell width 7/8 inchMesomphix friablisbrittle button, shell width 7/8 inch

June 2009 OutdoorIllinois / 9

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their shelled relatives.Many slugs actually dohave a small bit of shellremaining under thesurface of their skin,over the mantle area,but it does little to pro-tect the animal.Instead, slugs haveevolved other means ofstaying hydrated andprotected. For one,their bodies producemore mucus than mostshelled snails do, and itoften is quite thick andresists evaporation. Some slugs curl upwhen provoked, while others writheand secrete other chemicals that tasteoffensive to predators.

SlimeSnails exude a slime trail, visible as

a silvery path on the surface afterthey’ve crawled over it. Slime, or

mucus, is an impor-tant adaptive mecha-nism to help the snailsurvive. Its body andfoot have mucousglands, which secretethe mucus as it moves.The mucus makes iteasier for snails toglide over any surface,

even if rough or sharp. In fact, a snailcan even crawl over the edge of arazor blade without getting cut.Another benefit of mucous trails is

that snails can sense and follow them,allowing them to follow other snails toareas of food or for breeding. Like ahoming mecha-nism, the trailsprevent snailsfrom wanderingoff the knownpaths of safety.

SensesSnails’ bodies

have well-devel-oped tactileresponses, one ofthe most important adaptations for soft-bodied animals. With one touch of yourfinger, most will quickly retreat intotheir shells.Two pairs of tentacles (often mistak-

enly called “antennae”) on the snail’shead contain chemoreceptors at theirtips. The longer pair also usually bearseye spots that don’t form images butare capable of detecting changes inlight. The lower pair is shorter, andused primarily for chemoreception,guiding the snail to food or to congre-gate with other snails. Snails have noears, but they can detect vibrations.

ReproductionMost of the land snails of Illinois are

hermaphrodites, organisms that haveboth male and female reproductiveorgans. Although they are capable of

self-fertilizing, most seek a mate withwhich they exchange sperm to fertilizethe partner’s eggs. Eggs are depositedin soil, or under logs or woody debrisand then abandoned. Depending on thespecies, embryos develop and hatch inone to a few weeks, emerging as smallsnails with just one whorl of shell. Juve-nile snails begin to feed immediately.

FeedingMost land snails are generalist herbi-

vores, consuming the detritus (decom-posing plant material) of their environ-ment. They also are known to consumesoil directly and some fungi.Snails eat by means of a structure in

the mouth called the radula, a chitinous(similar to fingernail tissue) ribbonbearing fine teeth, with which it raspsoff bits of food.A few snail species in Illinois are car-

nivorous, either in part or as specialists.Haplotrema con-cavum, the gray-footed lancetoothsnail, feeds uponother land snails.Its radula is spe-cially adaptedwith barb-liketeeth, whichenable it to tearthe flesh of othersnails. With this

elongated “neck,” it crawls inside theshell of its prey as it tries—unsuccess-fully—to withdraw from the lance-tooth. In addition to its carnivorousfeeding abilities, these snails locatetheir prey by following mucous trails.

Land Snail EcologyWhat makes land snails so important

to Illinois’ ecosystems?Snails serve an essential role in the

breakdown of plant material becausethey assimilate nutrients such as calci-um, magnesium and potassium, andpass them to higher trophic levelswhen they are consumed by predators.Snails are only one step above the

Land snails glide on a large, muscular foot

that contracts in waves in the direction

the animal is moving. Glands in the foot

produce mucus that aids in movement.

Found in moist, decidu-

ous woodland habitats,

the Carolina mantleslug

does not invade gardens.

The only predatory land snail in Illinois,

the gray-footed lancetooth (above) extends

its long neck into the shell of other snails.

Mesodon zaletustoothed globe, shell width 1 inch

Mesodon zaletustoothed globe, shell width 1 inch

Haplotrema concavumgray-footed lancetooth snail, shell width 3/4 inchHaplotrema concavumgray-footed lancetooth snail, shell width 3/4 inch

Philomycus carolinanusCarolina mantleslug, body length 2 in.Philomycus carolinanusCarolina mantleslug, body length 2 in.

10 / OutdoorIllinois June 2009

The Fragile Existence of LandSnails in IllinoisFrank Collins Baker, a famous mala-

cologist (someone who studies mol-lusks), lived in Illinois during the 1930sand wrote the “Fieldbook of Land Snailsof Illinois,” published in 1939 (IllinoisNatural History Survey, Manual 2).Although most of the species names areoutdated, it remains a useful guide.Notable from Baker’s range descrip-

tions, as well as other field studies,land snail diversity and numbersappear to be on the decline. Manyspecies that once occupied habitats inthe Chicago area no longer exist(according to recent observations bythe author and malacologistsStephanie Clark, Chicago Academy ofScience and JochenGerber, The FieldMuseum), and somethat Baker personallyobserved in southernIllinois have not beenrecorded again. Habi-tat destruction is like-ly the main cause.Because snails areslow-moving organ-isms with a “survive-where-you-are” strat-egy, they cannot escape clearing oftheir habitat, nor can they toleratechemicals that run off our roads andlawns. Some species occupy very

specific microhabitats, and tend to bevery patchy in their distribution—another factor that can be detrimental

if their niches areharmed.Certainly, more

research is needed onland snails and theirhabitat requirements,but awareness is criti-cal for anyone interest-ed in preservingwildlife.Land snails, and the

vital role they play inecosystems as a food source for manyanimals, deserve our respect, admira-tion and efforts to preserve habitat.Preservation of natural habitats

is necessary if snails are to thrive inIllinois.

The rare carinate pillsnail possesses a

flying saucer-shaped shell (left). The

author’s (right) research focus has been

the land snails of Illinois.

base of the food chain, meaning thereare plenty of predators relying on snailsfor their dietary needs. A great diversityof animal life feeds upon land snails,from insects to lizards and snakes, sala-manders, birds and mammals. Somespecies of fireflies consume snailsexclusively during their larval stage.Many birds rely on snails for the

extra calcium they provide. One studyshowed that during egg-laying season,female wild turkeys consumed as muchas 40 percent more snails than normal.The snails provide calcium and othernutrients vital to the formation of shellsand embryos.Some speculation exists that the

decline of some snail predator speciesis related to the decline of land snails. AEuropean study suggests the decline offorest birds is related to the decline ofsnails, whose populations have beenadversely affected by acid rain.

Marla L. Coppolino is an artist and bio-logical illustrator, and has worked in var-ious positions in biology and malacolo-gy, including collections assistant for theMollusk section of the American Muse-um of Natural History in New York. Landsnails were Coppolino’s research focusfor her Master of Science degree fromSouthern Illinois University at Carbon-dale. She currently is a technical writerin Ithaca, New York.

Euchemotrema hubrichticarinate pillsnail, shell width 3/8 inchEuchemotrema hubrichti

carinate pillsnail, shell width 3/8 inch

Deroceras reticulatumgray fieldslug, body length 2 in.Deroceras reticulatumgray fieldslug, body length 2 in.

Inflectarius inflectusshagreen, shell width 1/2 inchInflectarius inflectusshagreen, shell width 1/2 inch

June 2009 OutdoorIllinois / 11

Triangular-shaped bristles on the sur-

face of its shell are used to identify the

shagreen (right). Believed to have origi-

nated in western Europe, the gray field-

slug (below) has invaded many parts of

the world and has become a garden pest.

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