Fleas
False colour scanning electron micrograph of a flea. CDC image.
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
(unranked):	Eumetabola
(unranked):	Endopterygota
Superorder:	Panorpida
Order:	Siphonaptera Latreille, 1825

The flea (Siphonaptera) is an insect which lives on many animals and sometimes humans. Fleas are ectoparasites and drink the blood of the animal they bite.

Fleas live outdoors in sand or tall grass, and jump to any passing animal and lay eggs. Flea bites are usually red bumps and they itch.

There are many species of flea such as dog fleas, cat fleas, human fleas, northern rat fleas, and the oriental rat flea. During the Middle Ages, the oriental rat flea spread a bacteria that caused the bubonic plague, also known as the Black Death or Black Plague. This was a huge epidemic much more severe than today's bird flu. The oriental rat flea was infected by the bacteria Yersinia pestis.