Fleas are tiny little insects, roughly around 3mm in length, with long back legs designed for jumping long distances. They don’t have wings, but they can travel quite far just by jumping. Fleas are typically reddish-brown or brown in color with thin, flat, hairy-looking bodies (that get fatter as they gorge themselves) and mouthparts like tiny siphons. These tiny siphons are designed to help them stab and suck the blood of their host.

Fleas have six legs and are more than able to jump large distances as they move from host to host. Their color helps them blend into the fur or hair of their host, while their thin, flat shape helps them move easily through thick fur. They have a hard exoskeleton and the “hair” on their bodies points backward. By design, this feature is meant to better help anchor them to their host.

Fleas may or may not have eyes, as they usually navigate their host based on their sense of smell and their antennae. Though adult fleas are small, they can be seen with the naked eye and are often found moving through an animal’s fur as they feast.

There are over 2,000 species of fleas worldwide, with 300 species residing in North America, there are only two species that seem to be most common in cats and dogs. One is the cat flea, or ctenocephalides felis, and the other is the dog flea, or ctenocephalides canis. There are also rat fleas, human fleas, raccoon fleas, rabbit fleas, and more.

Although all species have a specific host they prefer, it doesn’t stop them from feeding on other types of hosts. This means that the cat flea can affect dogs and the dog flea can affect cats and either type of flea has no problem feeding on humans or other animals, either. Dog and cat fleas both carry the parasite that creates tapeworms, and the oriental rat flea is a carrier of the bubonic plague.

Other Flea Species

Even though the most common types of fleas found in North America are the domestic cat and dog flea species, there are others to be found. In addition to the oriental rat flea (scientifically known as the xenopsylla cheopsis) that prefers feeding off rats, there is also a rabbit flea (or spilopsyllus cuniculi) found on both wild and pet rabbits, and the sticktight flea.

The sticktight flea is also called the tropical hen flea (or echidnophaga gallinacea) and feeds mainly off of poultry. There is even species of fleas that loves feeding on humans. One is called the human flea (or pulex irritans) and the other is called the false human flea (or pulex simulans). Both love humans as their host, but in a pinch are happy to feast on dogs, cats, and pigs too.

Because these two flea species are so closely related, you will often find the human flea and the false human flea in close proximity to each other. Both of these flea types can be found on dogs and cats, as well as wild canines quite regularly.

In North America, when someone has a flea infestation in their home with one of their pets, the most likely culprit is the domestic cat flea. In Europe, the dog flea is most often the culprit. However, someone can develop a flea infestation of any species of flea, no matter where they are. It’s just not as common as the cat and dog flea species.

The Life Cycle of a Flea

The life of a flea progresses through four stages:

1. Fleas start as an egg.
2. The egg turns into a larva.
3. The larva turns into a pupa.
4. Ultimately, you have an adult flea.

The only stage of a flea you will likely see on your pet is the adult stage. The other stages tend to happen elsewhere, such as the yard, or in carpet and bedding inside your home.

Note that an adult flea only accounts for about 1% of the flea population found near you, either in your yard, your home, or both. That means that for every one adult flea you find sucking your pet’s blood, you can rest assured there are at least 99 more of the little bloodsuckers percolating in the other stages of life around your house and yard, waiting to transition into adults.

A flea experiences a complete metamorphosis during the four stages of life and the entire process can take anywhere from two weeks to as long as eight months. Factors like humidity, temp, and food that’s available all play a role in how quickly the metamorphosis happens. Adult fleas much prefer warmer weather with a bit of humidity. In ideal conditions, a single adult female flea can lay upwards of 10-50 eggs. That works out to about 2000 potential eggs during the span of a flea’s potential lifespan of 60-100 days. Many of those eggs will grow into fleas that will reproduce and it’s easy to see how infestations can happen so quickly.

Once an adult flea hatches, the only goal it has is to feed. It has to feed within a week or it may die, although some can survive much longer in the right conditions and environment. Once the flea feeds and gets a belly full of blood, they move on to mating with another flea to perpetuate the life cycle.

Though it doesn’t usually happen within the first 24-36 hours, once a flea feeds and breeds, it’ll start laying eggs. This usually happens within the first week unless they are unable to feed. Once the female flea starts laying her eggs, she’ll start laying roughly 20-30 eggs per day for about 3-9 days.

The female will lay her eggs on her host, because she needs to continue feeding as she lays the eggs to keep her metabolism up. Most of the eggs the female flea lays will be laid in your pet’s coat or hair. Eggs are sticky, whitish in color, and wet at first, but they quickly dry out and then wind up falling off the host.

This is why flea eggs are often found on the floor, in the yard, on furniture, or on your pet’s bedding. In fact, most of the egg, larvae, and pupae population will be found close to your pet’s favorite spot to nap and lay.

When you crunch the numbers, it’s astonishing to realize that you can be fighting off an infestation of a quarter of a million fleas in just thirty days, all in varying stages of life. Unfortunately, because of how the life cycle progresses, that’s exactly what makes fleas so hard to get rid of. It takes anywhere from 1-10 days for flea larvae to come forth from a flea egg, and it can take even longer in poor conditions as the larvae waits for the best time to hatch.

Once the larvae are hatched, this is the most vulnerable stage they go through other than adulthood. They look like little, prickly earthworms or ugly maggots. They are white in color until they feed, which must be done within three days or they will die.

Once they feed, they turn brown. They like dark places, moderate temps, and high humidity to survive and thrive. Regardless of color, this stage is when they are easiest to kill. They can’t survive water or full sunlight, which is why they seek dark places. However, this larvae stage only lasts maybe a week to just under two weeks.

Once larvae go through their molting processes, the larvae spin cocoons to enter the pupae stage. Pupae are a whitish color and very sticky to help them camouflage themselves with debris from their environment. Though pupae are tougher than larvae, they can still die during this stage if the humidity is low or if they are exposed to insecticides.

The pupae process can take five days up to two weeks to fully develop. However, once the cocoon is spun and two weeks have passed, they can sit and hibernate in that stage for several days up to six months with no food. This is how they survive conditions that may not be ideal, such as extreme temperatures.

Essentially, this is a pre-adult state where the flea just waits for the right time to emerge fully-formed. So, no matter how many adult fleas and larvae you manage to eradicate, there are always more, ready and waiting to begin the whole process once again. It’s a nasty cycle that can be difficult to interrupt and defeat. When a flea is ready to emerge from it’s cocoon, it will do so because of some kind of pressure they have detected.

This might be pressure from heat or might be pressure from the host animal if it lays down on the cocoon. They just need the right trigger to emerge and begin to repopulate, even if all adult fleas and larvae have already died, which sometimes happens in homes where there was a flea infestation, but no host to feed on for a while.

Fleas emerge from their cocoon and find their host using touch and by senses. They can sense carbon dioxide, light, and air currents, which all work together to give them a general direction in which to jump and attach themselves to their host.

Unfortunately, it’s difficult to get a flea infestation under control, because of their life cycle. You need a flea control solution that doesn’t merely address your pet’s adult fleas, but also works to control the flea during its other stages of life.

What are common signs that my dog has fleas?

Your furry friend may need a dog flea treatment if you notice changes in behavior or appearance. Here are some common symptoms to look out for:

• Heavy scratching from irritated or dry skin
• Hair loss or your pet’s fur becomes noticeably thin
• Skin inflammation from flea saliva after flea bites
• Flea dirt or flea feces in your dog’s fur

If you’re unsure, quick use of a flea comb can help identify flea droppings or other clues to their skin-related concerns.

How Dangerous are Fleas?

Fleas can carry tapeworms and cause a tapeworm infestation in your pet when your pet bites and chews and accidentally swallows a flea. You may not even realize your pet has tapeworms unless he starts scooting or you notice his appetite is down. Thankfully, tapeworms aren’t usually transmittable to humans, although you should always be safe and wash your hands after playing with or handling an animal.

Additionally, fleas can cause other serious diseases, such as FAD (flea allergy dermatitis) which is basically an allergic reaction to flea saliva. The flea saliva from a flea bite triggers a rash that will make your pet itchy and miserable. That rash can progress into something that requires treatment from your vet to resolve, including secondary infections.

Other problems a pet can experience with a heavy infestation of fleas is anemia in dogs. Fleas are tiny bloodsuckers. When there are many of them all over your pet, then they consume more blood than you might realize. This is especially prevalent with pups and kittens, because their bodies are much smaller and weaker than an adult dog or cat. If you notice your pet’s gums look pale and they seem to be behaving in a lethargic manner, anemia may be the reason.

And finally, fleas can cause humans some trouble as well, due to bacteria they carry. The bacteria bartonella henselae causes what’s known as cat scratch disease (CSD), which can be passed on to humans through a cat bite or even petting a cat with fleas.

CSD isn’t fatal but can cause significant problems and discomfort as well as pain. Dogs can get an infection too from a different species of the bartonella bacterium, which can cause significant pet health issues like liver and heart disease, along with more minor health issues such as vomiting and lameness.

As you can see, fleas aren’t cute, and they aren’t healthy for your pets or for you. They are tiny little pests that cause untold mayhem if left unchecked. If you think your pet may have a flea problem, it’s important to get started with treatment sooner rather than later, so you can begin to effectively combat this scourge and eradicate them from your home and yard.

Sources:

1. Clark, ByMike, and Mike Clark. “What Fleas & Bites On Dogs Look Like & Home Remedies To Get Rid Of Them.” Dogtime, Dogtime, 25 Jan. 2018, https://dogtime.com/dog-health/54279-fleas-bites-dogs-look-like-home-remedies-get-rid.
2. petMD. “PetMD.” PetMD, 21 Mar. 2016, www.petmd.com/dog/parasites/evr_multi_common_fleas_dogs_cats.
3. “Pictures of Fleas: What Do Fleas Look Like?” Orkin.com, www.orkin.com/other/fleas/what-do-fleas-look-like/.
4. “What Do Fleas Look like?” What Do Fleas Look Like & How To Get Rid of Them | No Bite Is Right, www.nobiteisright.ca/en/parasites/fleas/.