[3] Pulex irritans is a holometabolous insect with a four-part lifecycle consisting of eggs, larvae, pupae, and adults.

Larvae eventually form pupae, which are in cocoons that are often covered with debris from the environment (sand, pebbles, etc.).

The larval and pupal stages are completed in about 3–4 weeks when the adults hatch from pupae, then must seek out a warm-blooded host for blood meals.

They are dark brown in color, are wingless, and have piercing-sucking mouthparts that aid in feeding on the host's blood.

Fleas are a pest species to their hosts, causing an itching sensation that results in discomfort and leads to scratching in the vicinity of the bite.

Fleas can spread rapidly and move between areas to include eyebrows, eyelashes, and pubic regions.

The earlier a patient seeks medical care and receives treatment that is appropriate for plague, the better their chances are of a full recovery.

People in close contact with very sick pneumonic plague patients may be evaluated and possibly placed under observation.

[5] Despite the origins of P. irritans, it is now a cosmopolitan species, most likely due to the fur trade after the 18th century, and pet transport in more recent decades.

[7] The use of morphometric data, which is often the method for flea identification, showed no significant levels of divergence between the two populations.

Human and cat fleas from Europe and the Mediterranean were studied and show such great variation within their own species that their taxonomy should be reevaluated based on mitochondrial gene heterogeneity.