Spider beetles feed on decomposing or dry animal and/or plant organic matter. They are often found in buildings that have been inhabited by rodents and/or birds. In the case of rodents, the spider beetles feed on old bait, droppings, and hair. In the case of birds, they feed on feathers and droppings. Spider beetles prefer hard-to-reach areas, but they can be found almost anywhere food is available, and sometimes in tremendous numbers.