The lower tentacles are for tasting and smelling. Slugs also have a fold of skin, known as a mantle, on their back, with a breathing pore at the edge of this mantle. The size, color, location of the mantle, and color of the mucous are used to identify the different species. Some species of slugs secrete a clear slime, others a milky slime. Most land snails have lungs, but some live in moist areas and have gills. Most snails have thousands of microscopic tooth-like structures on a ribbon-like tongue called a radula, which they use to rip apart food. Many snails are herbivorous (plant-eaters), but some are carnivores (meat-eaters) or omnivores (eating plants and meat). Near the front of the body on the right side is a hole or slit called a pneumostome, which is the opening that leads to the slug's single lung. The largest structure is the foot, which runs the length of the slug. The underside of the foot is called the sole. The gray garden slug is very common and about one inch long. Terrestrial slugs and snails, by contrast are primarily in a subgroup known as the pulmonates that actually have a mantle cavity that has become connected to the circulatory system (vascularized) to function as a lung. Slug biology, ecology and pest status Slugs are soft bodied gastropods (Mollusca) with rasping mouthparts and two pairs of tentacles (Figure 1). The animal's eyes are located on the uppermost, longer pair, called ocular tentacles; the lower pair, called peduncular tentacles, have a sensory function. A slug breathes through a small hole called a pneumostome that is located on its mantle, the. Slugs are very efficient in the use of their body parts. The mantle encloses and protects the slugs internal organs, pumps water and filters out food, and stores eggs while they mature. The body is primarily made up of water to avoid desiccation. They have a mantle cavity which protects internal organs such as a lung (pneumostome) Want to know your way around a slug? Let's start at the top. The mantle is a fleshy lobe that secretes the shell in snails. It is vestigial in most slugs but useful for identification. The keel (carina) is a backbone-like ridge that runs the length of the back in some slug species. That blowhole on the side is called the pneumostome and leads to the slug's lung. Slugs can swing their two.