Fleas are small, wingless parasites that feed on the blood of warm-blooded animals, including pets and humans. While often associated with pets, fleas can also bite humans and are notorious for transmitting diseases, making them one of the most common disease carriers. Despite their lack of wings, fleas have powerful legs that allow them to jump long distances. Although tiny, they are visible to the naked eye. Their backward-pointing bristles help them move quickly through fur, hair, and feathers, making them difficult to eliminate.