Fleas

Definition

Small, wingless, laterally compressed insects of the order Siphonaptera, obligate ectoparasites of mammals and birds. Adults possess enlarged hind legs adapted for saltatorial (jumping) locomotion, piercing-sucking mouthparts for hematophagy, and comb-like setae (ctenidia) that aid retention on host pelage or plumage. Larvae are apodous, vermiform, and feed on organic debris in host nests or bedding rather than blood. Fleas undergo complete metamorphosis (holometabolous development) and include species of major veterinary and medical importance as vectors of plague (Yersinia pestis), murine typhus (Rickettsia typhi), and myxomatosis.

Etymology

From Old English flēah, flēa, of Germanic origin; cognate with Dutch vlo and German Floh.

Example

The oriental rat flea (Xenopsylla cheopis) transmits Yersinia pestis between rodents and to humans, while the cat flea (Ctenocephalides felis) is the most common ectoparasite of domestic dogs and cats worldwide and a frequent cause of flea allergy dermatitis.

Synonyms

• Siphonaptera

Related Terms

• Ectoparasite
• Hematophagy
• holometabolous
• ctenidium
• Vector
• Plague
• Xenopsylla
• Ctenocephalides
• pulicosis
• myiasis

Usage Notes

Technically refers to the order Siphonaptera (~2,500 described species), though 'flea' is sometimes applied loosely to unrelated jumping arthropods (e.g., 'water fleas' are cladoceran crustaceans, 'sand fleas' are typically amphipods or tungaid fleas depending on region). Specialists distinguish 'true fleas' (Siphonaptera) by their compressed bodies, jumping legs, and blood-feeding adults. The term is plural in common usage; singular 'flea' refers to an individual specimen or species.