Flea Ctenocephalides felis

Most of an infestation is in the carpet, not on the pet — the bulk of a flea population, eggs, larvae and pupae, sits in carpets, soft furnishings and skirting gaps rather than on the animal that brought them in. Bites appearing around ankles after time away, or after moving into a previously pet-owning property, are the usual giveaway.

Treatment has to cover the whole space the pet uses, not just where it sleeps, and needs pupae accounted for since they can lie dormant for weeks before hatching — which is why a single quick spray rarely finishes the job on its own.