Growing up in the country meant finding snail shells all the time. In the woods, by the creek, in the creek, everywhere. I've seen snails. I've seen slugs. I've marveled at both with childlike curiosity. But it wasn't until I moved into my house in the suburbs of the south side of Indy that I saw armies of snails (live ones, not simply shells).
The first gastropod I saw at my house was a particularly large leopard slug (Limax maximus), also known as great gray garden slug and tiger slug. These guys grow up to about 4 inches (sometimes more) and, as their common names suggest, are gray (sometimes yellowish) and spotted.
Then I started to witness my massive army of snails coming out after the long, brutal winter. When I say "army," I mean anywhere from 10 to 20 in sight (I tend to exaggerate a bit). On humid or damp nights, I'll see my snails. Two nights ago I counted 16 within a 1' by 3' area just outside my sliding door. Being the curious girl that I am, I began to study them to see where they were hiding during the day.
There is a huge crack between my patio and house. Many of my snails use this crack as their barracks. Others are fond of the area underneath my deck. Still others were hiding under a cooler and cardboard we had by the house.
So, the girl that some have claimed may have an army of spiders at her command now has an army of snails. Spiders and snails: unlikely allies in the fight against whatever.
Control
Yes, snails and slugs can be quite problematic for home gardeners. If you've got them in your yard, forget about hostas or strawberries! However, opening up the area they're in to allow air circulation and reduce the moist, damp habitat they require can greatly discourage slugs away from a particular area. Beer or fermented foods make efficient, homemade slug traps (although I'm not a fan of killing anything!).