Order Siphonaptera is a group of insects commonly known as fleas. Fleas are parasitic insects that feed on the blood of their hosts, often pets and other mammals. Synonyms for Order Siphonaptera include "flea order," "Siphonaptera insect order," and "blood-sucking insect order." There are over 2,500 species of fleas worldwide, with the most common one being the cat flea. Fleas can transmit diseases to their hosts, including bubonic plague and typhus. They are also known for causing allergic reactions in some people and pets. Flea control is important for the health and well-being of both humans and animals.