Pennsylvania Land Snails
Photo(s): Larry Watrous
Anguispira alternata (Say, 1816)
Common name: Flamed disc
Although most of Pennsylvania’s land snails display subtle colors, the flamed disc is a vivid pinwheel of deep red on a pale yellowish background. The radiating streaks decorate a shell that can be as big across as a nickel. Its thin orange mucus is reminiscent of a spicy chili sauce.
The flamed disc is a widespread member in a family of heavily-ridged land snails. The ridges can be felt with your fingertips, but are best observed under the microscope. This snail is approximately 20mm wide and 12mm tall (Pilsbry, 1948), and has a thin-lipped aperture and an umbilicus almost a third of its width.
Variations in the shape of the flamed disc’s shell appear to be common (Pilsbry, 1948), and have led to questions about the taxonomy of some populations. Some have a relatively angular periphery, though most typical flamed disks are more weakly angular. And, a relative (A. fergusoni) found in the eastern portion of Pennsylvania has a similar color pattern, but has clear mucus.
The flamed disc is often found around logs and rocks, and Hubricht (1985) stated that it has a wide habitat tolerance, being also found on roadsides, railroads, and vacant lots. It ranges from the Midwest to Maine (Hubricht, 1985). It is a relatively good climber, often found at night on the trunks of American beech (Fagus grandifolia) or other trees, where it is presumably grazing upon bark-dwelling algae.
Land snails that have been implicated as intermediate hosts for various mammalian parasites include the flamed disk. For example, the cervid brainworm Parelaphostrongylus tenuis may be spread by the flamed disk, which is attracted to deer scat (Bird and Garvon, 2005).
Ken Hotopp, 10/8/05
Development of this site was supported by the generous contributions of Pennsylvanians to the Wild Resource Conservation Fund.