Garden and plants in Italian

Le lumache mangiano l’insalata di notte cannot be carried into English without settling something the Italian leaves open. « Snail » and « slug » are two separate words, and the line between them is drawn by one thing only: the shell. A shell makes it a snail, no shell makes it a slug, and no speaker of English would use either word for both. Italian keeps the same two creatures and sorts them differently. Strictly, la lumaca is the one without a shell and la chiocciola the one with it, but in ordinary speech lumaca covers the pair, and a gardener complaining about le lumache has said nothing about shells. La chiocciola is left with the work that needs the shape rather than the animal, which is why it is the name Italian gives the sign in an email address. The rule therefore runs one way only. Going in, both English words are safe as lumaca; coming out, the shell is a detail the sentence has to supply, because the noun will not.