Fleas are small, wingless insects that live as external parasites, feeding on the blood of warm-blooded animals. They thrive in diverse environments, from their hosts’ fur to hidden corners of a home. Understanding where fleas reside and how they interact with their surroundings helps manage their presence.
On Animal Hosts
Adult fleas primarily inhabit their hosts, feeding on blood for survival and reproduction. Common hosts include household pets like dogs and cats, but fleas can also infest other animals such as rodents and wildlife. While fleas often specialize in one host species, they can feed on other animals, including humans, if their preferred host is unavailable.
Once on a host, adult fleas use specialized mouthparts to pierce the skin and ingest blood. Female fleas require blood meals to produce eggs, laying between 15 to 50 eggs daily on the host’s fur. These eggs are not sticky and typically fall off into the surrounding environment as the host moves. Adult fleas can live for several weeks to months on a host under ideal conditions.
Fleas commonly gather around the hips, hindquarters, neck, and base of the tail on dogs, and near the neck on cats. Their bites can cause irritation, itching, and lead to skin conditions or transmit diseases. Small or young animals, such as kittens or puppies, can develop anemia from severe flea infestations.
Within the Environment
While adult fleas live on hosts, the immature stages—eggs, larvae, and pupae—are predominantly found in the environment. Flea eggs, which are tiny, white, and oval-shaped, detach from the host and disperse into areas where the host spends time. These eggs often settle into carpets, bedding, upholstered furniture, and cracks in flooring. Outdoors, eggs can be found in shaded, humid areas like under bushes or in leaf litter.
Flea larvae hatch from eggs within 1 to 12 days. These blind, worm-like larvae, measuring about 1.5 to 5 mm, avoid light and burrow into dark, sheltered spaces. They feed on organic debris, including skin flakes, hair, and “flea dirt,” which consists of dried blood excreted by adult fleas. Common larval habitats include carpet fibers, cracks and crevices in floors, pet bedding, and upholstered furniture.
After 5 to 20 days, larvae spin silken cocoons and enter the pupal stage. These cocoons are sticky and accumulate dust and debris, providing camouflage that makes them difficult to spot and resistant to many treatments. Pupae can remain dormant for weeks to several months, waiting for favorable conditions or a host’s presence to emerge as adult fleas.
Locating New Hosts
Adult fleas possess sensory abilities that allow them to detect and locate potential hosts from their environmental hiding spots. They do not rely on sight, which is typically poor. Instead, fleas are attuned to environmental cues that signal the presence of a warm-blooded animal.
Attractants for fleas include body heat, carbon dioxide exhaled by breathing, and vibrations or movements. These signals prompt fleas to emerge from their cocoons or hiding places. Once a potential host is detected, fleas use their powerful hind legs to jump onto the animal. They can leap to latch onto fur or clothing.
Fleas often enter homes by hitching rides on pets returning from outside, or on humans’ shoes or clothing. Once attached, they settle into the host’s fur, begin feeding, and initiate the reproductive cycle.