Slugs lack this feature. Both possess a muscular foot for locomotion, gliding over surfaces aided by secreted mucus. · snails carry a large exterior shell they can completely retract into. Weve done the research! Many slugs have either a reduced shell or an internal vestigial shell that offers little defense. · all gardeners see them, but what are the difference between them? Snails and slugs are both gastropod mollusks, and unlike most gastropods they are terrestrial i. e. Were exploring the differences between snail vs slug and explaining both. Slugs and snails are generally distinguished by the presence of a large exterior shell on the back of snails. While both cause similar damage, key differences between them can help identify which is harming your garden and offer guidance on how to manage them. Most snails — including land snails , freshwater snails and sea snails — use this external shell for protection and moisture retention. · true snails have an external, typically coiled shell made largely from calcium carbonate that protects soft tissues and helps retain moisture. · typically feeding at night, snails and slugs prefer dark, damp spots. · slugs and snails belong to the same biological class, gastropoda, part of the phylum mollusca, highlighting their common ancestry. Slugs lack an external shell; Some have a small internal plate or a reduced shell under the mantle (these are called semi- slugs ). Jump in to read about slugs and snails ! · what are the differences between slug vs snail ? This mucus helps retain moisture and protect their soft bodies.