What do fleas look like?

A common question we receive here at Flea Bites 101 is, “What do fleas look like?”

Fleas are one the most common types of annoying pests and are by far the most annoying and dreaded when it comes to causing discomfort in dogs and cats. Though slightly less annoying for humans nowadays, fleas were once a harbinger of plagues, disease, death and outright misery for humans.

Therefore, understanding what a flea looks like is an important step in protecting your pets and family from a flea infestation.

Most Fleas Look Alike to the Naked Eye

One may be lead to believe that only one type of flea is responsible for these pesky acts.

However, a frightening fact is that there are over 2,000 species of fleas around the globe, and an estimated 300 of these species have been found in North America alone. Different flea species have different preferences on the hosts that they select to feed on. Fleas are ecto-parasites (parasites residing outside of the host’s body) that rely on the blood of their host to survive.

Adult fleas are approximately 2.5 mm in length and appear dark in color (brown or reddish brown). Fleas are wingless but have six long legs that allow them to jump long distances from host to host for feedings.

With that said, unless you get up close and personal under a microscope and inspect the anatomical differences, most fleas are going to look indistinguishable from the next to the naked eye.

Anatomy of the Flea

Although fleas are tiny, individuals that have previously observed them on pets or themselves can easily recognize them. To the naked eye one may assume that the exoskeleton of a flea is smooth, but in reality the flea’s body is covered in tiny hairs that run in the direction opposite of its head.

The flea’s body is squished vertically flat.

If you were looking at a flea head-on and staring him down as you prepared to unleash holy hell and drop flea bombs, foggers, sprays and even some napalm, while you are at it, it would almost be like looking at the edge of a sheet of paper.

This sleek, “aerodynamic” design allows fleas to easily navigate you dog’s hairy forest of a coat.

The flea’s body is also covered in hard plates called sclerites, which makes squishing it with one’s hand quite challenging. Their body has backward facing hairs that allow them to hold on to the furry coat when the cat or dog violently shakes their body or scratches their skin with their paws. They are almost like seat belts that keep them nice and snug. The flea also has spines around the head and mouth but the number of spines vary depending of the species of the flea.

Under a microscope one would be able to gain a much better view of the flea. From the view of a microscope one would notice that the external body structure of a flea consists of a head, thorax and abdomen.

The mouth parts consist of the epipharynx and lacinia, while the leg structure consists of the coxae, trochanter, femora, tibiae and tarsus. A review under a microscope can also identify the species of flea that one is currently viewing, which isn’t easy to determine from a naked-eye observation.

Brief Overview of Various Flea Species

As previously stated there are over 2,000 types of fleas that plague the world, and are host specific. A few common types that are most likely to be encountered are human fleas, dog fleas and cat fleas.

Human Fleas

Fleas that are human specific species do exist, although not as common thanks to improved hygiene. Human fleas are most commonly found on pigs and other animals nowadays. Human fleas may look the same to the naked eye, but a closer look under a microscope reveals the difference.

Dog Fleas

Dog fleas can often be caught from raccoons, possums and livestock. The same holds true in vice versa for the cat flea, who is scientifically referred to as Ctenocephalides felis. Dog fleas can infect humans as well, but they are not very common in North America.

Cat Fleas

Cat fleas are the most common type found in North American on household pets. Both cat and dog fleas carry the tapeworm parasite which can even more of a nuisance if left untreated. If your dog has fleas, it is most likely infested with cat fleas, believe it or not.

As an aside, the names for fleas are kind of odd, don’t you think? Human fleas are seldom found on humans, dog fleas are seldom found on dogs and cat fleas are almost always what you will find on your pooch.

How Does the Flea Eat and Suck Blood?

The mouth of the flea is adapted to easily suck blood from a host. Several mouth parts come together to form a needle like drinking tube. This drinking tube can easily pierce the skin and allow the flea to feed. Anatomy of the feeding structure is as follows:

  • Two laciniae that bear several rows of teeth and are similar in appearance to a saw, pierce the skin. They can also combine to form a saliva channel.
  • The epipharynx is like a needle in which it surrounds the laciniae and forms a puncturing agent known as stylet.
  • The stylet is supported by the prementum and labial palps.  

When a flea bites its host blood travels from the host’s blood vessels, through the epipharynx of the flea and into its body. Like a syringe suction is needed to remove the blood from the host’s body, and in a flea suction comes from the pumps in the gut and mouth of the flea. The saliva of the flea also prevents the blood from coagulating and keeps the pierced wound open for continuous feeding and blood sucking.

This is how the pesky insect feeds on its host and creates skin problems. Please see the following page with information about what a flea bite looks like.

We did not cover the leg structures of the flea and how it is capable of jumping incredible distances relative to its body size. However, since this article is getting kind of long we may save that for a separate article all of its own since they are pretty fascinating in their own right.

What do fleas look like? Now you know more about what a flea looks like and how their bodies function than you ever probably wanted to know and should have no problem answering that question.