The yellow slug, Limacus flavus. The picture shows 3 mature L. flavus resting on the ground beneath a (removed) flower pot. The small white spherical object to upper left is a slug egg. The colour range - from greenish to yellow, is typical. Also visible at the rear of the two slugs to the right is the short yellow keel. L. flavus is also called the cellar slug, or the tawny garden slug. It is a large pulmonate gastropod mollusc, and nocturnal in its habits. Rarely seen, it is widespread and common in Southern parts of Britain, and often congregates, as here, under pots or paving stones, sometimes in large groups, seeking the damp cool conditions it prefers. "Cellar slug" denotes that it may enter houses. Its food preference is decaying matter: it does little damage to plants in the UK. In other parts of the world it is a serious pest following introduction.