Fleas are small, wingless insects, typically 0.1 to 0.32 cm long, that feed on the blood of mammals and birds. Their tough bodies are equipped with bristles and spines that help them move through the host's fur or feathers and anchor themselves. The flea life cycle includes egg, larva, pupa, and adult stages. Flea larvae feed on organic debris in the host's nest, and adults rely on blood for nourishment. Fleas can cause severe skin inflammation and itching and transmit diseases such as plague and typhus. Flea control involves treating both the host and its environment with insecticides or growth regulators.

What do fleas look like?

Fleas are small, wingless insects ranging from 0.1 to 0.32 cm in length. Their bodies are compressed to allow them to move through the hair or feathers of a host. They have a tough cuticle covered with bristles and combs of flattened spines that project backward to help them anchor themselves to the host. Fleas' mouthparts are adapted for sucking blood and include barbed stylets to help them penetrate the host's skin. Their most impressive adaptation is their highly developed jumping legs, which allow them to leap long distances. Though fleas are wingless, they have retained parts of the flight mechanism that have been incorporated into their jumping mechanism.

Fleas are small, wingless insects that feed on the blood of mammals and birds. There are roughly 2,000 species and subspecies of fleas, some of which, like the rat flea and mouse flea, have spread worldwide with the help of humans. Adult fleas can be found on the body of their host animal, but their eggs can be laid either on the host or in the host's nest or habitat. Flea larvae live in the host's nest, where they feed on organic debris. Rodents are the most heavily parasitized mammals because they build nests in holes, which favors the development of flea larvae. Animals without permanent homes tend to have fewer fleas.

How do fleas get food?

Fleas are small, wingless insects that rely on blood for nutrition. Adult fleas possess mouthparts adapted for piercing skin and sucking blood from mammals and birds. They have barbed stylets that aid in penetrating the host's skin and help them stay attached, especially for species that remain on the host for extended periods. After fleas consume blood, it passes quickly through their system. This process results in fecal matter that nourishes their offspring. This is essential for the metamorphosis of certain flea larvae.

How can fleas affect animals and humans?

Fleas can severely affect animals and humans, causing intense itching and skin inflammation. Constant attacks may lead to allergies, especially in humans. Flea bites can cause blood loss and transmit diseases such as bubonic plague and murine typhus, with rodents often serving as reservoirs of infection. They can also act as intermediate hosts for tapeworms, and transmit viral diseases. Certain fleas, like the jigger flea, burrow into the skin, causing intense itching and potential secondary infections.

How can infestations of fleas be prevented or controlled?

Fleas can cause severe skin inflammation and intense itching. They can also transmit diseases, such as plague and murine typhus. Prevention and control of fleas require treatment of both the host animal and the environment. To control fleas: * Treat pets Use commercial dusts, sprays, dips, or aerosols that contain an insecticide or growth regulator on pets. Fleas in some regions have become resistant to some insecticides, so new materials are needed. * Treat the environment Apply insecticides or growth regulators to the pens and habitats of affected animals to control larvae and adult fleas away from the host. Repellents can effectively prevent flea attacks. * Address rodent infestations Because rodents can carry diseases transmitted by fleas, controlling rodent populations is crucial. It is ethical to control flea infestations to protect animal and human health and prevent the spread of disease.

flea

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Images

Diagram showing the flea life cycle with labeled stages: white oval eggs, wormlike larvae, pupa within a cocoon, and a detailed adult flea, arranged in a circular sequence.

Detailed labeled illustration of a cat flea (Siphonaptera) showing its segmented body with head, thorax, and abdomen, along with key features such as mouthparts, eye, genal and pronotal combs, spiracle, clasper, and segmented legs with coxa, femur, tibia, tarsus, and tarsal claws.

At a Glance

flea summary

flea

insect

Also known as: Siphonaptera

Written by

Robert TraubAll

Fact-checked by

Britannica Editors

History

General features

Fleas are small, wingless insects with a tough cuticle bearing many bristles and frequently combs (ctenidia) of broad, flattened spines. The adult flea varies from about 0.1 to 0.32 cm (0.039 to 0.13 inch) in length and feeds exclusively on the blood of mammals (including humans) and birds. With about 2,000 species and subspecies known, the order is still a small one compared with many other groups of insects. However, it is widely distributed with some—such as the rat flea and the mouse flea—having been carried all over the world by humans. Native species of fleas are found in polar, temperate, and tropical regions.

Importance

Infestation by fleas may cause severe inflammation of the skin and intense itching. Although many animals acquire partial immunity after constant or repeated attacks, individuals (especially humans) can occasionally become sensitized after exposure and develop allergies. Species that attack people and livestock include the cat flea (Ctenocephalides felis), the so-called human flea (Pulex irritans), the dog flea (Ctenocephalides canis), the sticktight flea (Echidnophaga gallinacea), and the jigger, or chigoe, flea (Tunga penetrans). Poultry may be parasitized by the European chicken flea (Ceratophyllus gallinae) and, in the United States, by the western chicken flea (Ceratophyllus niger).

Certain fleas that feed primarily on rodents or birds sometimes attack people, particularly in the absence of their usual host. When rats are dying of bubonic plague, their hungry fleas, themselves infected with plague bacilli and seeking food elsewhere, can transmit the disease to humans, especially in buildings heavily infested with rats. The Oriental rat flea (Xenopsylla cheopis) is the most efficient carrier of plague, but other species of fleas (e.g., Nosopsyllus fasciatus, Xenopsylla brasiliensis, Pulex irritans) can also transmit the disease to people. Although there are occasional cases of plague in tropical and some temperate regions, the disease in humans can be controlled by early diagnosis and antibiotics. Plague (sylvatic plague) is a widespread disease in hundreds of species of wild rodents throughout the world and is maintained in those populations by fleas that parasitize these animals. More than 100 species of fleas are known to be able to be infected by the plague bacillus, and an additional 10 species are implicated as carriers of the classic type of urban plague. (See infection.)

Fleas, particularly Xenopsylla cheopis, are thought to be the principal carriers of murine (endemic) typhus, a rickettsial disease of humans. As in plague, rats and mice are the sources of infection. Fleas are considered important in the maintenance and spread of many locally restricted infections among rodents and other mammals, including tularemia and Russian spring-summer encephalitis. Fleas transmit myxomatosis, a viral disease of rabbits, which is used deliberately to control rabbits in areas where they are severe pests (e.g., in Australia). Fleas are probable carriers of a filarial worm of dogs and serve as the intermediate host of a common tapeworm (Dipylidium caninum) of dogs and cats and occasionally children. If heavily infested, animals can suffer severe damage or be killed by the effects of flea bites and the resultant loss of blood. Fleas are subject to parasitism by external mites, internal nematode worms, and bacterial, fungal, and protozoan infections.

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Britannica Quiz

Animal Group Names

The female jigger, or chigoe, flea (not to be confused with “chigger,” a larval mite) burrows into the skin of its host, generally on the feet, and lives within a cyst that forms around it. Intense itching accompanies the development and enlargement of the cyst as the abdomen of the pregnant flea swells to the size of a pea; secondary infections may constitute serious complications.

flea

General features

Importance

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