| |
Ed Thompson |
Hendersonia
occulta (Say, 1831)
cherrystone drop
Family
Helicinidae
Order Neritopsina
The cherrystone
drop is an exciting land snail to see in Pennsylvania because
it is uncommon and has unusual features. Its shell is very
like a cherry pit in size and shape (approximately 6 to 8mm
in diameter), but having an aperture for the snail’s
soft body to emerge, of course. The shell can be a variety
of subtle colors, including a cinnamon red, or pale yellow,
green or blue, while older shells are bleached white.
The animal
is quite different from other Keystone State land snails in
its anatomy and taxonomy. The cherrystone drop is a Neritopsine,
so individuals can be male or female, rather than hermaphroditic
like the rest of Pennsylvania’s land snails. It has
an operculum, a tiny cover to close the aperture when retracted,
and eyes at the base of its tentacles instead of at the tips.
Most of its relatives are tropical.
The
cherrystone drop is a calciphile, found only on calcium-rich
soils of steep limestone glades or hardwood forests in the
Appalachian Mountains, though found on flatter grasslands
in the Midwest where it also occurs. It can be very patchy
in its distribution, with large expenses of apparently suitable,
yet unoccupied, habitat. Colonies may be dense, with dozens
of individuals per square meter.
Pleistocene
deposits show that this snail was once much more common in
North America, but is now know from only sporadic locales
in a dozen states (e.g. Hubricht,
1985). In Pennsylvania, H. occulta is found
at only a few sites in the southwestern quarter of the state.
It was first found in Pennsylvania in 1831 or ‘32 by
James S. Craft a Chartiers Township landowner (MacMillan, 1950).
Ken Hotopp,
1/2/06
|
|
Development
of this
