Adult: 1–6 mm
Larva: 2–3 mm

Identification marks

Fleas are shiny, wingless insects that live in the nests of mammals and birds. They are usually quite black in colour and have flat sides. Fleas move around by leaping.

The larvae are usually white and have no legs.



Many animals have their own species of fleas. A flea of a specific host animal may try to feed on other animals or humans. The larvae live in the host animal’s nest and feed on organic waste.

The human flea (Pulex irritans) is no longer seen in Finland.  Furthermore, cat and dog fleas have not been observed in Finland for decades. Fleas of birds or squirrels can, however, also bite humans.

A chicken flea (Ceratophyllus gallinae) is a common visitor in birds’ nests and can easily spread to humans. Up to 2000 fleas can spread over from one bird’s nest every year, and then spread onto cats and dogs from vegetation and be carried indoors by the pets.


A flea bite results in a reddish bump, which itches. Cortisone and antihistamine lotions are used to treat the bites, if necessary.

Prevention and extermination

Birdhouses should be cleaned during the winter, before the fleas hatch from their cocoons in the spring. Any waste from the birdhouse should be burned.