Pennsylvania Land Snails

Haplotrema concavum (Say, 1821)

Common name: Gray-foot lancetooth
Family Haplotrematidae
Order Stylommatophora

The gray-foot lancetooth is a fearsome predator among land snails. It is large and versatile – from 11 to 21mm in diameter (Pilsbry,1946) and able to attack other snails by entering the aperture or rasping a hole in the shell. However, this is snail is not exclusively a snail predator, eating nematodes or plants as well.

The shell of this lancetooth looks like it might have been made from a coil of rolled clay because its whorls are tubular. It is flattened - about half as tall as it is wide - and the umbilicus is wide. The shell is a somewhat glossy gray, pale yellowish or pale greenish color, and the animal is gray.

Commonly found in Pennsylvania forests, this animal occurs throughout the eastern United States and Canada. Although there are 16 Haplotrema species in the West, it is one of only two representatives of this genus in the East (Roth,1991).

The gray-foot lancetooth hunts by following the slime trails of other land snails. Once it has latched onto its victim, whether by entering through the aperture or a hole it has rasped in the shell, it may drag the prey to a sheltered location to feed (Atkinson,1998). Presumably this reduces its own exposure to predators. In an experiment, Pearce and Gaertner (1996) showed how the gray-foot lancetooth preferred snail prey that were larger, with larger apertures and thinner shells.

Ken Hotopp, 4/3/06

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