Insects and their Allies  

Siphonaptera: fleas

Fleas are small, wingless insects ranging in size from approximately 1-10 millimetres in length depending on the species. Almost everybody, especially those with cats or dogs will be familiar with these small biting insects and will have either seen them or the effects of their nuisance bites. Fleas can be recognised by the following features:

Ctenocephalides felis
Ctenocephalides felis (PULICIDAE)
  • Laterally compressed bodies
  • Piercing-sucking mouthparts
  • Enlarged hind legs adapted for jumping
  • Strong tarsal claws adapted for holding onto their hosts
  • Backward pointing hairs and bristles for ease of movement through the hair of a host
  • Small antennae which tuck away into special groves in the head

The species Ctenocephalides felis (above) is the introduced cat flea but can survive on a wide range of host species. The larvae of all fleas appear grub-like and are usually found in the nests of their host or other areas where they commonly rest.

Life Cycle
Fleas mate on their host animal and lay their eggs either onto the animal where they fall to the nest or directly in the nest. The small larvae hatch from the eggs and do not begin to feed on blood like that of their parents but consume the dead skin and other dirt and dust from the host animal. The larvae develop through 3 instars and when fully grown spin a silken cocoon and pupate in the nest of the host. The vibrations of a host often trigger the emergence of the adult flea from the pupal case, enabling it to immediately find a host and begin feeding. The complete life cycle may take from several weeks to many months depending on the species.

Pulex irritans (human flea)
Pulex irritans (human flea)

Adult fleas feed on the blood of their host and although most fleas are adapted to one particular animal, many are not host specific and will move to other animals if their preferred host is unavailable. Fleas are very adaptable and are also able to withstand unfavourable conditions and can live for many days without food.

Fleas are always found close by their hosts, either in direct contact such as among the feathers or hair or within their nests. Fleas are found in almost all habitats in Australia where there is a ready host and many native species of flea are closely associated with native marsupials and rodents. The main introduced species are also associated with animals that have been introduced to the country such as the cat flea (Ctenocephalides felis) the dog flea (Ctenocephalides canis) and the rat flea (Xenopsylla cheopis).