Fleas are bloodsucking insects that, as adults, feed only on fresh blood directly from their mammal or bird host. Because they typically take multiple blood meals each day and frequently move among hosts, fleas can be significant disease vectors. Some animals (including some humans) are highly allergic to flea salivary secretions and a single flea bite can produce severe itching.
Only the adult flea stage lives on the host, so successful flea control is dependent on eliminating egg, larval, and pupal stages in the environment. Because adult fleas must feed on host blood, treating the host can successfully reduce adult flea numbers.
Different flea species attack different hosts, although some flea species can be found on a wide variety of hosts. Rodent fleas generally remain in the nest, moving onto the host during the day when the nocturnal host is asleep to feed. Other fleas, such as cat and dog fleas, remain on the host continuously. Knowing the flea’s identity is important in order to allow prediction of its behavior and determining how to best control it.
All fleas are wingless but most have strong, highly developed hind legs that allow them to jump distances many times their body length. Most adult fleas have spines on their bodies that catch on hair (or feathers), making removal from the host difficult. Fleas are small insects, generally less than 1/8 inch in length, even after taking a blood meal.