Siphonaptera, commonly known as fleas, are small, wingless insects that belong to the order of insects characterized by their jumping ability. They are ectoparasites, meaning they live on the outside of their hosts, primarily feeding on the blood of mammals and birds. Fleas have a flattened body, which helps them move easily through the fur or feathers of their hosts. Fleas are known for their rapid reproduction, with females laying hundreds of eggs in their lifetime. They can transmit various diseases, including the bubonic plague and typhus, making them significant pests in both domestic and wild environments. Their life cycle includes egg, larva, pupa, and adult stages, allowing them to thrive in various habitats.