Terrestrial Snails

Zonitoides arboreus (Say, 1816)

Quick Gloss

This is a very common snail and widespread snail.  Turn over a piece of firewood that is resting on the ground and you are likely to find it.  It is often found under loose bark.  Dead elm trees are a great spot to find them.  I have also found them underneath the plastic sleeves used to protect newly planted trees.

This is a pretty distinctive small (5 mm diameter) snail.  It has a smooth dark brown shell with no reflected lip.  It has an open umbilicus.  Perhaps the most distinctive characteristic, however, is the two-toned nature of the snail itself.  The upper part is a dark gray color, and the lower part including the base of the foot is very pale, almost white.

I have seen some photos of other snails that have a distinct two-tone look, but certainly none of them are as common as this one or look quite like it.

This snail is apparently one that can be numerous enough to be a crop pest.

Hubricht's distribution map for this species shows it in the southernmost counties of Florida, Texas, and California, and the northernmost parts of Maine, Michigan, Minnesota, and Washington State.  His map shows it recorded in about 1/4 of Iowa, including primarily eastern and northeastern Iowa.  I believe this snail is likely to be present in all counties of Iowa and that the distribution map is more a reflection of where Iowa's snails have been surveyed and collected rather than where this snail is found.

Of the three Zonitoides species in Iowa, Z. limatulus has a more sculpted surface, and Z. nitidus is slightly larger and has a more rounded aperture.

The photograph to the right shows the open umbilicus.