Siphonaptera Click to enlarge image
Flea (Order Siphonaptera) Image: Andrew Howells
© Australian Museum

Fleas belong to the Order Siphonaptera.

What do fleas look like?


  • 0.5 mm - 10 mm in length but most are shorter than 5 mm.


  • Very thin as if pressed from the sides.
  • Covered with hairs and spines directed backwards, some in comb-like formations.
  • Appears hard.


  • Very short, held in a groove hence often difficult to see.
  • Never longer than body.


  • Very small or absent.


  • For piercing and sucking.


  • Absent.


  • Six legs.
  • Hindlegs enlarged and modified for jumping;
  • Have claws modified for clinging to feathers and hair.

Abdomen tip:

  • Cerci (tails) absent.

Where are fleas found?

  • On mammals and birds (rarely) among hairs or feathers.
  • Few are found on semi-aquatic animals such as the platypus, but never on marine mammals.

What do fleas do?

  • Fleas are external parasites. They maybe found alone or in large numbers on suitable hosts.
  • When disturbed they jump. They can jump incredible distances.
  • They feed on blood.
  • They are active during the day.

What looks similar?

  • Flies that do not have wings can be mistaken for fleas. Unlike fleas, wingless flies are never thin as if pressed from the sides.
  • Lice differ from fleas in that they are flattened as pressed from above, do not jump when disturbed, and can occur on fully aquatic hosts.