Most people have heard of fleas and probably know what they are. Those with pets may be particularly familiar with this pesky intruder.

What many people may not know is that there are several types of fleas found in the United States and throughout the world. The more common of these include:

  • cat fleas
  • dog fleas
  • human fleas
  • oriental rat fleas

Cat fleas are the most common in North America, but they are found on dogs and cats alike.

Appearance / Identification

What Do Fleas Look Like?

Cat Flea
Cat Flea
dog flea
Dog Flea

Photo credits: CDC.gov

Fleas are very small in size, usually about 1/8’ long or even smaller.

They are dark brown, reddish–brown, or black. They can appear reddish–black when they are full of blood.

Fleas have a flattened appearance, as if they had been squeezed from both sides.


Fleas will attach themselves to a host for survival. They will crawl through an animal’s fur and attach themselves to the host.

In addition to household pets, this can also include wild animals, rodents, chickens, rabbits, squirrels, and even people.


What do fleas eat?
As ecto-parasitic insects, adult fleas feed on the blood of other animals. Fleas typically feed multiple times per day, with mated females gaining the ability to lay eggs only after consuming a blood meal. They need specific proteins from the blood.

After emerging from the pupal stage of development, new adults can survive for up to a week without eating. Once fleas take their first blood meal, the they can live for months or even years before feeding again.

While adults feed on the blood of host animals, larvae consume the dried blood excreted by adults. Larvae also feed on organic particles found in the cracks of floors or bedding areas of animals.


Where Do They Like to Live?
Fleas can live either indoors or outdoors, though the insects develop quickest in warm, relatively humid environments and are therefore more commonly found inside in temperate zones.

During the larval and pupal stages of the life cycle, fleas often take shelter in carpeting, pet bedding, and the cracks between floorboards.

Outdoors, flea larvae and pupae overwinter in similarly protected areas. Only adults live on host animals, which the insects detect by sensing body heat, movement and vibrations, and exhaled carbon dioxide. Fleas gain access to host animals by jumping up to the host.

How do they enter the house?
Fleas can enter the home in many ways, even if your pet is not or only rarely allowed outside. They can hop in from your yard, hitch a ride on you, or even be left over from previous inhabitants (larvae can remain dormant for astonishingly long periods of time under a variety of conditions).

Life Cycle

Female fleas lay up to 8 eggs after every meal. These are deposited on or between hairs of the host animal or in the animal”s bed. The eggs are not attached, but will fall off and land in carpets or on furniture.

Within several days or up to two weeks, larvae will hatch and feed on fecal material from the adult fleas.

After a period of a couple weeks or months, the larvae spin a cocoon.

They will emerge as adults many weeks later. At this point, the new adults repeat the same process of finding a host.

If a flea infestation is present, a homeowner will likely need to treat both the pet and the house.

Infestation Signs

Pet owners will often observe a pet”s constant scratching when fleas are present. A flea infestation can also occur in a household without pets.

Flea eggs, which are white and visible to the naked eye, are a telltale sign of an infestation. Adult fleas also regularly produce defecations of dried blood, which look like dark, cylindrical flecks measuring about a sixteenth of an inch long. The presence of flea bites on humans or pets indicates a potential infestation, as well.

Do Fleas Fly?
Fleas cannot fly, but are able to jump great distances.

Flea Dangers

Problems Caused by Fleas

When fleas pierce the skin of host animals to gain access to blood meals, the parasitic insects often cause an itchy red welt to form at the site of the bite.

flea bite on person
Photo credit: https://extension.missouri.edu/

Dogs and cats, especially ones with sharp claws, are at risk of scratching the flea bites excessively and creating open wounds prone to infection.

More seriously, fleas are traditionally known as transmitters of various diseases that have adverse, and sometimes fatal, effects on humans and pets alike. Fleas can spread the bubonic plague which, though rare today, was responsible for the deaths of roughly 25 million people in Europe during the 14th century. The parasites can also transmit murine typhus to humans by first feeding on the blood of an infected rodent.

Additionally, since tapeworms sometimes use fleas as intermediate hosts, dogs and cats may unknowingly ingest the tapeworm larva contained within an infected flea. The tapeworm will then continue developing in the digestive system of the cat or dog.


Indoors, homeowners can help prevent flea infestations by vacuuming regularly to remove any eggs that might be in the area. Residents should also make sure to bathe and groom pets on a regular basis and wash pet bedding frequently. Pet owners should take advantage of veterinary treatments used to prevent and kill fleas on dogs and cats.

Outdoors, homeowners should keep lawns trimmed and eliminate potential habitats for rodents, which often carry fleas into the yard.

For serious infestation problems, consider using the services of a pest control specialist. Professionals specializing in pest control have experience in eliminating infestation and can access a wider range of products used to combat flea infestations effectively.