The article is written by Pavlo Chaika, the chief editor of the "Piznavayka" magazine. Since its founding in 2013, Pavlo Chaika has been dedicated to popularizing science in the world. The main goal, both of the magazine and of this article, is to explain complex scientific topics in a simple and accessible language.



  • Description and Characteristics

  • Lifespan

  • Habitat

  • Diet

  • Species

  • Reproduction

  • Life Cycle

  • Home Fleas

  • How to Detect Fleas in an Apartment?

  • Flea Bites

  • What Diseases do Fleas Carry?

  • How to Get Rid of Fleas?

  • Interesting Facts

  • References and Further Reading

    Fleas are one of the most famous small parasitic insects. Most of the harm and trouble they cause to our pets: cats and dogs, but can also be dangerous for humans, since in some cases fleas can be carriers of dangerous diseases, such as pseudotuberculosis, listeriosis, and tularemia. What are the habits of these little parasites? What does a flea look like, where does it live, how to deal with fleas? Read this in our article.

    Description and Characteristics

    What does a flea look like? The body length of a flea is only 1-5 mm, but sometimes females of fleas can have much larger sizes, up to 1 cm, especially after intensive feeding. Due to their diet, the size of their abdomen increases, and the flea increases in size. The largest fleas that are larger than 1 cm are parasitic on moose and deer.

    A flea’s body consists of the abdomen and head; it is covered with a strong chitinous cover. If you’ll look at a flea under a microscope, you’ll see how much the body of this insect is flattened from the sides. The evolution justifies such a flea’s body. Due to this, a flea can easily penetrate animal fur, bird feathers, and even the folds of human clothing.


    What color are fleas? A flea’s color can be reddish, yellowish, and dark brown or completely black.

    A flea does not have wings and does not know how to fly, but it jumps perfectly. The fleas enter the body of animals only with the help of high and distant jumps, which are carried out due to the strong push of the second and third pairs of their legs.


    The flea is also covered with numerous spikes and bristles, which are scattered throughout the body. Due to this structure of the body of a flea, it is very difficult to comb it out, pull it out or bite it. You can destroy a flea only by crushing it on a hard surface.

    A flea’s eyes are located on the head. There are antennas behind their eyes; they help male fleas to feel the females during the mating season. These antennas are immersed in small antennae fossae.


    Fleas have a piercing-sucking type of oral apparatus. A flea bites through the host’s skin (on whose body it parasitizes), expands the wound and releases saliva there, which prevents blood coagulation. Then flea plunges into the wound, trying to get to the blood vessels. Feeding on blood, fleas fill their stomach, which may increase in size.

    Besides this, all fleas have a special sensory organ – pygidium, which is located in the back of their belly. The tactile hairs of pygidium are capable of sensing even the slightest fluctuations in the air, warning the flea of potential danger.

    A female flea has reproductive organs consisting of an ovary, an oviduct, and an ovule, while males have a copulative organ – a genital claw.



    How long do fleas live? The lifespan of a flea depends on its species and habitat, and can vary from several months to three years. When the air temperature is more than 30 °C (86 °F), the life cycle of the flea is reduced by 40%. At low temperatures, the flea’s lifespan, on the contrary, increases since its development slows down.

    How long do fleas live without an animal or in general without a donor? Being outside the animal’s body, the flea is left without food. However, these insects can easily starve for a long period – 30-40 days. At the same time, a flea can live for several months, although such a starving flea reduces its activity.


    Where do fleas live? These insects are common everywhere, even in cold Antarctica, where they can successfully parasitize on the penguins and seals. Most of their species live in the temperate and subtropical zones of Europe, Asia, Africa, and both Americas. Fleas are active at any time of the year. They usually live near the nests and burrows of their potential donors: warm-blooded animals.



    What do fleas eat? Fleas eat only the blood of their donors, on whose body they successfully parasitize. Mammals are the main victims of fleas, especially mammals who live in ground holes or nests. Usually, fleas do not live on their master’s body all the time but jump there only to be supported by their blood. When they are not hungry, they jump into the litter of a hole or nest.

    Some fleas are associated with animals that generally do not have permanent housing. Such flea species are stationary parasites, that is, once on the host’s body, they no longer leave it. Such fleas include, for example, fleas that live on dogs and cats.

    Unlike mosquitoes (in which females are only bloodsuckers) both males and females fleas suck blood equally. The process of blood saturation itself can last from one minute to several hours. Sometimes fleas become saturated with blood in reserve, significantly increasing their abdomen.


    Stationary fleas need regular nutrition; this is another reason why they do not leave the host body. They wander freely in the skin of their victim in between meals.

    Most species of fleas can parasitize on different animals, for example, jump from a squirrel to a dog or cat. The only exceptions are fleas of bats, which need only bats as a host.


    Zoologists have identified up to 27 flea families; we will describe the most interesting of them.

    Human Flea

    The human flea is the most common among fleas; it inhabits everywhere. The human flea has a brown color and a length of 1.6-3.2 mm. Moreover, this flea can jump to a height of 30 cm and a half meter length. Unlike other fleas, a human flea has no chest and head teeth. It can parasitize on different animals, including humans. In addition to humans, the human flea is often found in animals that have close contact with humans: cats, dogs, and horses. The human flea is very dangerous, as it can be the carrier of the causative agent of the plague, cause pulmonosis – an itchy skin lesion.

    Human Flea

    Cat Flea

    Despite the name, this flea lives not only on cats, but also on dogs, rodents, and many other animals, sometimes even on humans. The cat flea has a short proboscis and a flat forehead, body length is 0.75-5 mm.

    Cat Flea

    Dog Flea

    This flea is a close relative of the cat flea, and can also live on dogs, and cats and other animals, including humans. The dog flea is similar to a cat flea in appearance and size. The only difference in lifespan, if a cat flea lives up to 2 years, then a dog flea is not more than 1.5 years.

    Dog Flea

    Southern Rat Flea

    This type of flea is especially dangerous, as it carries the plague. The southern rat flea lives everywhere; especially they are common in areas with a warm tropical climate. Females have a length of 1.8 to 2.7 mm, males are slightly smaller: from 1.4 to 2 mm. The southern rat flea may have a light or dark brown color. The southern rat flea usually parasitizes on rats and other rodents and lives in their burrows or nearby.

    Southern Rat Flea

    Penetrating Flea

    Originally from Brazil and Haiti, over time this flea was moved into Africa, India, and Pakistan, where it successfully took root. The penetrating flea has an oval-shaped body and a reddish-brown color with a white speck in the middle. The average body length of this type of flea is 1 mm, while it can jump to heights of up to 30 mm. The penetrating flea lives in the grass, from where it jumps on animals, birds, and humans.

    Penetrating Flea


    Fleas reproduce all year round under favorable environmental condition. Fleas will survive without problems at extremely low temperatures, but will not reproduce. Both partners must be saturated for successful breeding; hungry fleas will not reproduce.

    The female flea climbs onto the back of the male and draws his sexual claw into his seminal receptacle. Interestingly, the sexual intercourse in fleas can last several hours, while it takes 10-15 minutes to transfer the seed to fertilize the female.

    In some time after fertilization, the female lays eggs, which pass in small portions. Usually, fleas lay 1-2 servings of 4-10 eggs per day. The egg-laying process itself is very curious: the female pushes eggs out of herself, which sometimes fly to considerable distances from each other. This position of the eggs makes sense, since subsequently the competition between hatched larvae decreases.

    flea eggs

    Life Cycle

    Fleas are insects with complete metamorphosis, and their life cycle consists of the following stages:

    • an egg,
    • larva,
    • a doll,
    • imago (adult).

    Flea eggs are very similar to rice grains.

    flea eggs

    Egg development lasts approximately 14 days. Then, vermiform and translucent larvae appear from them. The flea larvae have no legs. They climb into the litter of the master’s nest. Flea larvae feed on rotting organics, skin epithelium, or the remnants of undigested blood in the excrement of their parents.

    The larva turns into a chrysalis after three molts. The stage of the pupa (depending on the type of a flea), can last from several days to several months. In some species of fleas at the stage of the pupa fleas spend winter, and the exit from the cocoon is timed to the onset of spring heat.

    Having appeared from a chrysalis, an adult flea, first of all, begins the search for a master.

    Flea Life Cycle

    Home Fleas

    Home fleas are not a separate type of flea, but simply fleas that have settled somewhere in a human house. They often get into the house along with animals on which they parasitize. Home fleas often like wool carpets, crevices behind skirting boards, soft toys, bedding.

    How to Detect Fleas in an Apartment?

    Finding these parasites is sometimes quite difficult due to the small size of fleas. A white sheet can be a good method for this. If you suspect fleas, it must be placed on the floor, and if the fleas present, then after a while small black spots will appear on the white sheet.

    Flea Bites

    Flea bites cause stitching pain at the moment of piercing the skin and a strong desire to scratch a bitten place. A characteristic swelling usually appears at the place of the bite, somewhat similar to that of a cigarette burn. After the flea has eaten and detached, the edges of the wound converge, preventing bleeding, and hemorrhage forms at the site of the bite.


    The main method of protection against small bloodsuckers is the destruction of fleas at home + prevention from them and other possible parasites.

    The reaction to the bites of these insects for each person can be individual: some people may have slight itching and swelling of the affected area that will disappear within an hour, while others may have red skin at the site of the bite, harden and peel off for a long time. You must definitely consult a doctor if this happens.

    What Diseases do Fleas Carry?

    As we wrote above, a flea bite can be dangerous, because fleas can be carriers of various diseases, including such serious and deadly ones as:

    • Bubonic plague,
    • Typhoid,
    • Encephalitis,
    • Hepatitis B, C,
    • Toxocariasis,
    • Tularemia.


    How to Get Rid of Fleas?

    If these parasites are wound up in the apartment, then the best remedy for fleas will be special insecticides that can destroy fleas even in the most neglected premises. Since fleas could not even physically eat poison bait, the means of dealing with them are made in the form of sprays, powders, and suspensions that affect the nervous system of fleas.

    When cleaning a room with aerosol preparations, it is necessary to temporarily evacuate all the inhabitants of the house, and then thoroughly ventilate the room and do a thorough wet cleaning.

    Among the best flea repellent for home:

    • Spray raptor with a pleasant smell of mint. It is safe and effective. Usually, two cylinders are enough to handle a one-room apartment.
    • Biorin is a professional drug that destroys not only fleas but also other insects and parasites.

    After the destruction of fleas, it is worthwhile to do general wet cleaning in the house, and in general to support cleanliness.

    flea repellent

    Interesting Facts

    • Fleas were so popular among the French nobility in the XVII-XVIII centuries that French aristocrats even had special items for catching them – “flea traps”.
    • Fleas were the cause of the terrible epidemics of the bubonic plague in the middle Ages, which claimed many lives. The plague fleas were carried by rats and mice.
    • Fleas are true jumping champions. A flea’s jump length can exceed the flea’s length by 100 times!
    • Serious scientific study of fleas for the first time was undertaken in the 19th century. A great contribution to their study was made by Charles Rothschild, a wealthy English banker, and entomologist. He also collected the world’s largest collection of different fleas, which is now stored in the British Museum.

    References and Further Reading

    • Wiley: The Insects: An Outline of Entomology, 5th Edition – Gullan, P.J.; Cranston, P.S.” www.wiley.com. Retrieved 11 November 2016.
    • Taylor, Sean D.; Cruz, Katharina Dittmar de la; Porter, Megan L.; Whiting, Michael F. (May 2005). “Characterization of the Long-Wavelength Opsin from Mecoptera and Siphonaptera: Does a Flea See?”. Molecular Biology and Evolution. 22 (5): 1165–1174. doi:10.1093/molbev/msi110. ISSN 0737-4038. PMID 15703237.
    • Jump up to: a b Fleas. Koehler, P.G.; Oi, F.M. Printed July 1993, revised February 2003. Provided by the University of Florida.
    • “Order Siphonaptera – Fleas”. BugGuide.Net. Retrieved 11 November 2016.
    • Jump up to: a b c d Crosby, J.T. “What is the Life Cycle of the Flea?”. Veterinary Parasites. About Home. Retrieved 4 November 2016.

    Author: Pavlo Chaika, Editor-in-Chief of the journal Poznavayka

    When writing this article, I tried to make it as interesting and useful as possible. I would be grateful for any feedback and constructive criticism in the form of comments to the article. You can also write your wish/question/suggestion to my mail pavelchaika1983@gmail.com or to Facebook.