Fleas can nest and hide in a variety of places in a house, but they typically prefer warm, humid, and dark areas. Here are some common places where fleas may nest in a house: Fleas can lay eggs and develop into larvae in the fibers of carpets and rugs. They can hide deep in the fibers where vacuuming might not reach. Fleas can hide in the crevices and cushions of furniture, particularly if it is upholstered or contains fabric. They can lay their eggs in pet bedding, and these eggs can hatch into larvae and pupae, making it a hot spot for infestation. Fleas can hide in small cracks and crevices in walls, floors, and baseboards. Fleas can also enter the house through cracks in the foundation, and if there are any outdoor pets, they can transport fleas into the house.