Snails and slugs are among the most bothersome pests in many garden and landscape situations. The brown garden snail (Helix aspersa) is the most common snail causing problems; it was introduced from France during the 1850s for use as food.
Both snails and slugs are members of the mollusk phylum and are similar in structure and biology, except slugs lack the snail's external spiral shell.
Snails and slugs move by gliding along on a muscular "foot." This muscle constantly secretes mucus, which later dries to form the silvery "slime trail" that signals the presence of either pest. Slugs and snails are hermaphrodites, which means all have the potential to lay eggs. Adult brown garden snails lay about 80 spherical, pearly white eggs at a time into a hole in the topsoil. They may lay eggs up to six times a year. It takes about 2 years for snails to mature. Slugs reach maturity after about 3 — 6 months, depending on species, and lay clear oval to round eggs in batches of 3 — 40 under leaves, in soil cracks, and in other protected areas.
Snails and slugs are most active at night and on cloudy or foggy days. On sunny days they seek hiding places out of the heat and bright light; often the only clues to their presence are their silvery trails and plant damage. In mild-winter areas such as southern coastal locations, young snails and slugs can be active throughout the year.
During cold weather, snails and slugs hibernate in the topsoil. During hot, dry periods or when it is cold, snails seal themselves off with a parchment like membrane and often attach themselves to tree trunks, fences, or walls.