The vile flea, just like the bed bug, is a blood-sucking vermin. Let’s take a look at some of the characteristics of those insects:


Fleas are small, dark-coloured, wingless parasites which reach up to 4mm in length. They have flat, oval-shaped bodies which allow them to jump over distances over 33 cm long. They have tube-like mouth-parts, suited for feeding on the blood of their hosts. There are several different types of fleas. The most common are:


Canine (dog) flea (Ctenocephalides canis)


Feline (cat) flea (Ctenocephalides felis)


Human flea
(Pulex irritans)

Feeding Habits

Fleas feed only on bird and mammal blood. Although different types of fleas prefer different hosts, they all bite humans. The main host of choice for the most common species are dogs and cats. Their saliva prevents the immediate detection of the bite. Later it causes severe irritation and itching. Adult fleas locate their hosts by movement, vibrations and animal breath (through warmth and humidity differences in the air, etc.). Fleas also have larvae which feed on organic and faecal matter. Although they are hatched blind, they can detect adult fleas’ excrements—a sign of a food source nearby.

Cause of Infestations

Fleas are transmitted by your pets or by different types of rats and mice. They attach to the fur of the animals from infested dirt or foliage. They usually live on the underbelly area. Once their host goes inside of your home, they transfer to your carpet, drapers, furnishings or indoor plants. Fleas thrive in warm, moist places. Low temperatures halt their developmental cycle. Summer is the season when most infestations occur.

Where do fleas live?

Depending on the stage of their life cycle, fleas choose to live in different conditions. The eggs are laid on an animal’s fur, from which they fall off onto the environment – furniture upholstery, carpeting, bedding, floorboards and floor cracks, wall crevices. They spend their larval and pupal stages in these shady and humid locations, only to return to the animal’s fur as adult fleas.

Flea Eggs: Dozens of them are laid directly on your pet’s fur every day and fall spread wherever your pet brings them, which means flea eggs can end up in your bedding, furniture, carpeting and even on top of appliances (if you have a cat, you can be sure of it).

Flea Larvae: They like dark, narrow and dusty spaces that offer protection during this immature stage. Flea Pupae are found only on floors and in-between carpet fibre. Despite composing just 10% of a flea population, they are the main reason why flea treatments often fail. Their hard water-tight cocoon is impervious to sprays and leaves vacuum cleaning as the only option for proper pest control. A thorough hoovering will at the same time remove some of the flea pupae, while the vibrations from it will cause the other half to hatch.

Adult fleas: As adults, fleas hide only on live hosts such as cats, dogs, rodents and any other furry mammal.

Where do fleas live outside?

In your yard and in wildlife, fleas live in high grass, sand, sheds and debris – places where they can find shade and humidity. These areas, such as the grass underneath a shrub, provide the perfect conditions for all three stages of the flea’s life cycle. From the egg lay to the cocoons – and that’s not all. Animals also prefer to go in the shade on hot summer days, and that’s the time for the newly hatched adult fleas to go for a snack!

Where do fleas live in the house?

In the house, fleas live in crevices, floor cracks, wall junctures, carpets, rugs, upholstery and any type of bedding. Something people often wonder is if fleas live in floorboards and tiles. As a matter of fact, they’re even harder to control on hard floors than on carpeting. It’s important to keep in mind that if you want to get rid of fleas in your home, you have to be very thorough and treat all these areas at the same you treat your pet. It may even take months to fully remove an infestation!

Where do fleas live on dogs and cats?

The most densely infested areas on your pets’ bodies would be around the neck, ears and underbelly.  An even better questions is where do fleas come from? A flea infestation can take place even if your pets always stay indoors, as your own vibration and heat can attract a flea while you are enjoying a picnic, fishing trip or just a stroll in the high grass. Nonetheless, humans cannot actually get fleas – not the common household fleas at least. There’s a species called the human flea, Pulex irritans, that lives on humans, pigs and other mammals that don’t have fur. Those are encountered only in the wild, however, and are different from the fleas found on your cats and dogs.


Look for the following signs of flea infestation:

  1. Live fleas: they jump on drapery, carpet, furniture and upholstery. You can recognise them by the fast manner in which they “disappear” and their dot-like appearance.
  2. Change in the behaviour of your animal companion: excessive licking, scratching or gnawing its fur, it might indicate your pet suffers from flea bites. In severe cases, dogs and cats can lose fur in infested areas of their skin.
  3. Small, reddish-black dots on bed linen: those are the excrements of these blood-sucking insects—dry blood deposits.
  4. Itchy, pinkish rash on your skin

Health Effects

flea bites

photo credits to Michael Voelker

Although fleas rarely feed exclusively on humans, flea bites can still pose a serious health hazard. Fleas are known to spread a variety of diseases, such as typhus, tularemia, bubonic plague, and cat scratch disease. Typhus and bubonic plague are notorious for their mortality rates. Still, it is not likely for a human to be infected with them in the UK (due to vaccination and high hygiene standards).

Cat scratch disease, is a common and real health threat. It is caused by the Bartonella henselae bacteria and puts people with a weakened immune system at serious risk. It can result in muscle pains, enlarged lymph nodes, reproductive issues and deep inflammations and infections.

Fleas are also know to transmit various kinds of tapeworms, especially between animals.

Flea Control

Professional flea fumigation includes the use of a variety of insecticides, such as pyriproxyfen and methoprene. Industrial vacuum cleaners are also used, as frequent hoovering kills up to 96% of adult fleas and completely exterminate young fleas. Diatomaceous earth is also used in flea control, though rarely suitable, as it fumes are toxic to pets and humans. Though inefficient, the use of baking soda remains a popular DIY-method. On theory it causes fleas to die of dehydration.


Pupae and larvae of fleas are resistant to most of the pesticides used in flea control. Recently, researchers have found strains of fleas immune to popular pesticides such as fipronil, fluvalinate, cyfluthrin and cypermethrin. Thus, usually professional treatment is required to guarantee a flea-free property.

In Society

Although not known at the time, fleas have been the main cause behind the bubonic plague epidemics. They swept through the Old World between 542 (the Plague of Justinian) and 1720 (Great Plague of Marseille). At the peak of the outbreak (1346-1353), the Black Death killed an estimated 75 to 200 million people in Europe alone. This lowered the Earth’s population at the time by 40%.

Watchmakers have used fleas as an interesting way to show off their skills. The XIX century saw the rise of flea circuses—shows where fleas were “performing” acrobatic feats. Watchmakers made them rope-walk, juggle and pull cars. They also dressed them in tiny clothing to impress the public. This form of entertainment disappeared shortly after WWII. Still, several flea circuses exist to this day. A notable example is the one at the annual Oktoberfest in Munich, Germany.

What to Do in Case of an Infestation

It is important to seek professional help should you suspect a possible infestation. Fleas are hard to battle on your own. Even if all adults die, there is a high possibility for the problem to return. Most domestic-level pesticides use dangerous toxic chemicals—something which most professionals avoid.

Images by: 1. Fritz Hauke, 2. Michael Wunderli, 3. Michael Wunderli

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