Editing Flea (section)

{{Short description|Insects of the order Siphonaptera}}
{{Other uses}}
{{Redirect|Siphonaptera|the poem|Siphonaptera (poem)}}
{{Good article}}
{{Use dmy dates|date=January 2017}}
{{Automatic taxobox
| name = Fleas
| fossil_range = {{Fossil range|Middle Jurassic | Recent}}
| image = Flea Scanning Electron Micrograph False Color.jpg
| image_caption = [[Scanning electron microscope#Color in SEM|Scanning electron micrograph]]
| display_parents = 3
| taxon = Siphonaptera
| authority = [[Latreille]], 1825
| subdivision_ranks = Suborders
| subdivision = * {{extinct}}[[Pseudopulicidae]]
* {{extinct}}[[Saurophthiridae]]
* {{extinct}}[[Tarwiniidae]]
{{Plain list|
* Ceratophyllomorpha
* Hystrichopsyllomorpha
* Pulicomorpha
* Pygiopsyllomorpha
}}
| synonyms = Aphaniptera
}}

'''Flea''', the common name for the [[order (biology)|order]] '''Siphonaptera''', includes 2,500 species of small flightless [[insect]]s that live as external [[parasites]] of [[mammal]]s and [[bird]]s. Fleas live by [[hematophagy|ingesting the blood]] of their hosts. Adult fleas grow to about {{convert|3|mm|in|frac=32|abbr=off}} long, are usually dark in color, and have bodies that are "flattened" sideways or narrow, enabling them to move through their hosts' fur or feathers. They lack wings; their hind legs are extremely well adapted for jumping. Their claws keep them from being dislodged, and their mouthparts are adapted for piercing skin and sucking [[blood]]. Some species can leap 50 times their body length, a feat second only to jumps made by another group of insects, the [[superfamily (taxonomy)|superfamily]] of [[froghopper]]s. Flea larvae are worm-like, with no limbs; they have chewing mouthparts and feed on organic debris left on their hosts' skin.

Genetic evidence indicates that fleas are a specialised lineage of parasitic [[scorpionflies]] (Mecoptera) ''sensu lato'', most closely related to the family [[Nannochoristidae]]. The earliest known fleas lived in the Middle [[Jurassic]]; modern-looking forms appeared in the [[Cenozoic]]. Fleas probably originated on mammals first and expanded their reach to birds. Each species of flea specializes, more or less, on one species of host: many species of flea never breed on any other host; some are less selective. Some families of fleas are exclusive to a single host group; for example, the Malacopsyllidae are found only on [[armadillo]]s, the [[Ischnopsyllidae]] only on [[bat]]s, and the Chimaeropsyllidae only on [[elephant shrew]]s.

The oriental rat flea, ''[[Xenopsylla cheopis]]'', is a [[Vector (epidemiology)|vector]] of ''[[Yersinia pestis]]'', the [[bacterium]] that causes [[bubonic plague]]. The disease was spread to humans by rodents, such as the [[black rat]], which were bitten by infected fleas. Major outbreaks included the [[Plague of Justinian]], about 540, and the [[Black Death]], about 1350, each of which killed a sizeable fraction of the world's people.

Fleas appear in human culture in such diverse forms as [[flea circus]]es; poems, such as [[John Donne]]'s erotic "[[The Flea (poem)|The Flea]]"; works of music, such as those by [[Modest Mussorgsky]]; and a film by [[Charlie Chaplin]].