Fleas: The Flea Life Cycle

cat fleas iStock_000001607683SmallWhen it comes to fleas, the saying “keep your friends close and your enemies closer” is, unfortunately, quite applicable. To protect your furry friends and keep those irritating fleas as far away as possible, try out this other wise saying: “Know your enemies better than you know yourself.”

In its short lifetime, a flea passes through many development cycles. It’s important to know about fleas at each of these stages so you can have a better chance of identifying them and acting fast to eradicate them. Several flea treatments will only treat certain stages of the flea life cycle so it’s also important to know that you have all the stages covered when you’re selecting a treatment for your pet.

Fleas: A Brief Life


An adult female flea is capable of laying over 20 eggs every day. With the right conditions (temperature, humidity, and blood supply), an adult flea can also live on a host for 2 to 3 months. Do the math and you’ll see that flea eggs can multiply extremely fast.

Under a microscope, flea eggs actually look similar to the oval, white eggs that we’d associate with poultry. However, these eggs are pliable rather than hard-shelled, and, to the unaided eye, they appear to be just small white particles about 0.5 mm in length.

Since flea eggs are small, round, and smooth, they will likely fall off their host. This means that, aside from being found on your dog, flea eggs can also commonly be found in pet bedding, and anywhere around the house, indoors and outdoors, where your pet spends time.


When a flea egg hatches it enters the larval stage of its life. The flea larva is about 1.5 to 5 mm in length. It is wormlike, has some hairs, and has a dark brown head and dark body coloring showing through its translucent exoskeleton. Although the larvae are blind, they are sensitive to light and will seek out dark spots. This means that they can be commonly found deep in the fur on your dog’s belly, under its tail, and in the creases of its inner thighs and legs. In the home environment, flea larvae can thrive in carpet, in crevasses in the floor and doorways, and in and under furniture. Outdoors, larvae will seek out shady, cool spots that are high in moisture.

Fleas stay in the larvae stage for one to two weeks. During this time they feed on the organic materials in their environment. If they have remained on a host in company with adult fleas, the larvae will eat the adult feces which are rich in undigested blood. They can also live off of flakes of skin and other materials.


When the larvae are ready, they will spin a cocoon in which they will transform into an adult flea. The pupa can be identified by its oblong shape and white color. It will be larger than a flea egg. The pupae have a sticky exterior and can collect dirt, making them hard to spot. This also means that they will not fall easily off your dog.

A flea is able to remain in the pupa stage for a surprising amount of time. Although seemingly inert, the pupa is sensitive to the ideal heat and humidity conditions. It is also sensitive enough to know when there is a host nearby and can emerge quickly enough to catch a ride. So, aside from acquiring fleas from other animals, your dog is also able to get fleas simply by being in a place where there are flea pupae lying in wait.

Adult Fleas:

Once it has emerged from its cocoon and leaped onto a host, the flea is immediately ready to start eating blood. After only two meals, the female flea will begin to lay eggs and start the cycle over again. Without a blood meal, however, the flea will not lay eggs and will only live a few days.

Because of their three pairs of legs in graduated sizes, fleas have amazing jumping abilities and can travel surprising distances. Fleas have backward facing spikes which make it difficult to extricate them from fur but relatively easy for them to move forward and burrow down towards your dog’s skin. Although fleas are a little hard to catch, it is not difficult to discover their presence. Your dog will begin to scratch more frequently, and you will be able to find flea feces in your dog’s fur, often mixed with flea eggs. The mix of black feces and white eggs is sometimes called “salt and pepper.” One test you can do to check if you’ve found flea feces is to take the black specks, put them on a paper towel, and drip some water over them. If the water residue is red, that will indicate that the specks are blood-rich flea feces.

Knowing the stages of a flea’s life will help you in identifying a flea problem, selecting the best treatment method for your pet, and taking preventative measures for the future. See future articles for specific information about treating your pet, your home, and yard for fleas, and selecting the best household and commercial flea treatments and deterrents.



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