They also have a second pair of antennae located at the lower front of the their body. This pair acts like a nose, picking up chemical smells. Both of these tentacles can telecope in and out as they move along the forest floor to protect them from damage when they bump into leaves and twigs. Sometimes as a slug is moving, you will notice a small hole, usually on its right side, near the front of the body. This hole is called a pneumostone .
Air enters the hole and passes into a small lung-like cavity.
This extra lung provides more skin area for the slug to breathe through. Most people think that a slug's cloaca is located at the back end of the slug, as it is in most animals. This is not true. The lump of material that often gets dragged behind the slug is actually dirt and leafy material which was collected by the slime and gets dropped off at the back end of the slug. The cloaca is located behind the pneumostone under the mantle so it cannot be seen except when the slug is getting rid of wastes.