Stagnicola elodes, S. reflexa and S. exilis. Stagnicola reflexa is actually a form of S. elodes that is one year older than individuals of most populations. In the middle of the last whorl of S. “reflexa” a lighter colored transverse stripe (a varix), marks the size of the shell when it over-wintered. As snails increase in size, the mantle secretes additional shell material at the edge of the mantle bordering the shell aperture. Thus, the shell also increases in size.
John B. Burch (photographer; copyright holder), Mollusk Division, Museum of Zoology, University of Michigan-Ann Arbor