Andrew,

How very true!  Vitta usnea is reported from St. Augustine, Florida, USA,
through the gulf states, to Mexico, Belize, Guatemala, Honduras, Nicaragua,
Panama, Colombia, Venezuela, and the Caribbean islands of Cuba, Jamaica,
Santo Domingo, and the Lesser Antilles to Tobago.  Reports of this species
from further south in French Guyana are probably cases of misidentified
Vitta zebra (Bruguiere, 1789), a common species in that area (but it would
be intriguing to investigate the area where they might meet and see if they
intergrade or crossbreed).  Although Vitta usnea maintains a fairly
consistent color and pattern, the shell shape does vary from the typical
elongate shape found in the north to a round globose shape from Mexico
southward: the so called Neritina reclivata floridana (Reeve, 1855);
Neritina reclivata rotundata von Martens, 1865; and Neritina sphaera
Pilsbry, 1931 - all presently considered synonyms.  Mienis (1985) reports
the occurrence of both the elongate and globose forms (in varying
concentrations) from Florida to Columbia, making any division into
subspecies all but impossible.  There is also variation in specimens from
the Caribbean Islands.  The species is found only on those islands with a
substantial river.  Cuban specimens are often lighter colored with dark
stripes on a light gray background.  The Caribbean Islands are also home to
the rare purple specimen.  One instance of this unusual color form has also
been reported from Texas (Ode, 1985).  And then we have Vitta piratica
(Russell, 1940), occurring alongside Vitta usnea from the southern Yucatan
Peninsula through Belize, Guatemala, Honduras and Nicaragua to southern
Venezuela and far northern Brazil.  Also on the islands in the Greater and
Lesser Antilles (Cuba, Santo Domingo, Trinidad).  Vitta piratica is often
considered a form of Vitta usnea, but if 50 shells of each were dumped in a
pile, anyone could separate them out with certainty (not only is the shell
pattern different, they shell itself is usually thick and heavy, like Vitta
usnea on steroids).  This is all plenty of material for a PhD, we just need
someone who wants to slug around in swamps and then do a bit of lab work -
for a few years!

Tom Eichhorst

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