C. hortensis is a simultaneous hermaphrodite. A mating couple approach each other and try to manoeuvre into position to shoot a sharp dart of crystalline calcium carbonate into the body wall of the other by forceful eversion of its containing dart sac . The dart is coated with mucus from a pair of branched mucus glands opening close to the opening of the dart sac. Lodi & Koene (2016) think the mucus, if injected, impedes the recipient’s reaction of destroying some of the sperm inserted so as to leave some ova to be fertilized by other individuals.
The dart has four vanes (1) that are thin at base and thicker and bifurcated distally, giving a cross section like a Maltese cross (2 dyed green). This differentiates adults of C. hortensis from C. nemoralis which has a dart with vanes thickest at base and tapering steadily distally giving a cross section of a simple cross.
For examination, a stereoscopic dissecting microscope at c.X20 is needed. Clear scanning electron microscope images can be seen at upload.wikimedia.org/wikipedia/commons/8/8e/Cepaea_horten…
The dart is very brittle and is often missing if there has been recent mating. A more reliably-present feature for differentiation of adults of the two species is the number of branches on the mucus glands.
