There are thousands of different types, sizes and colors of spiders found all over the world in nearly every type of habitat. Spiders rarely bite humans unless their nests or webs are disturbed. With the exception of a few species, the venom in spider bites is harmless to humans, but some individuals may be hypersensitive and can have a mild to severe allergic reaction when bitten. Spiders feed primarily on other insects, but larger species have been known to feed on small animals such as lizards, birds and millipedes. Spiders in your home can be a sign of a larger pest infestation, and their building of webs indoors can prove to be a nuisance for most homeowners when left untreated. The combination of good sanitation practices and a comprehensive pest control treatment program are necessary to eliminating spiders inside the home.