Unlike other insects, fleas go through four life cycle stages instead of the. The four life cycle stages are egg, larva, pupa, and imago, or adult. Adult fleas must feed on blood before they can become capable of reproduction. Fleas are also know for their agility, as their hind legs are well adapted for jumping; a flea can jump vertically up to 7 inches and horizontally up to 13 inches, making the flea one of the best jumpers of all known animals (relative to body size), second only to the froghopper.

• Fleas are tiny, wingless insects, usually dark colored.
• Their bodies are flattened on the sides, permitting easy movement through the hairs or feathers on the host's body (or in the case of humans, under clothing).
• The flea body is hard, polished, and covered with many hairs and short spines directed backward, which also assist its movements on the host, and their tough body is able to withstand great pressure, likely an adaptation to survive attempts to eliminate them by mashing or scratching.