The Life Cycle Of A Flea

  • Written By Dan Edwards on November 10, 2018
    Last Updated: December 17, 2020

As we have seen fleas are hardy parasites that are capable of multiplying rapidly in the right conditions. What starts off as one flea, can quickly become a large infestation in almost no time at all. It is important to understand the intricacies and timings of the flea life cycle, so that when it comes to fighting them, you can be prepared to hit them at every stage of their development.

What Are Flea Life Cycle Stages?

The flea life cycle is really not very long when compared to that of other insects. Essentially, a flea life cycle has four different stages: egglarva, pupa and then adult flea. This entire cycle can be completed in a couple of weeks. In some cases, environmental changes can cause the process to be delayed by months. Fleas eggs and larvae are able to become dormant for long periods if the conditions outside are not conducive to hatching.

Life cycle of a flea

Female fleas lay eggs while they are attached to a host. The eggs then fall off the host and onto the ground, remaining there until they hatch. In most cases, they will hatch within two to 12 days. Once they have hatched, they become larva, which survive in the ground or within carpets. They eat their own shedded skin, organic waste and the bodily waste of adult fleas. In warm weather they will stay at this stage for around 4-24 days, if it is cold, they can remain in the larval stage for up to 200 days.

Flea Eggs On Carpet
Flea eggs in the carpet – CC Image courtesy of Denni Schnapp

Once the larva is ready, it will create a cocoon and become a pupa while it develops into an adult flea. Once an adult, the flea will remain roughly the same size for the rest of its life. This final stage can take about one to two weeks, but just like the other stages, can be delayed by unfavorable conditions.

Finally, the adult flea will leap and hatch onto a passing host where it will feed.

What Do Fleas Look Like Throughout the Stages?

When examined up close, fleas look very similar in basic structure to other insects. They have six legs and three body segments which comprise a head, thorax and an abdomen. Adult fleas are flattened from the sides, which helps them to move through the fur of the host. They have a dark brown color but can also look reddish or light brown, depending upon the amount of blood they have recently consumed.

Adult Flea
Adult Flea
Flea Overhead View
CC Image courtesy of Lynette Elliott

Adult fleas are around 1/12 to 1/8 inches long. Female fleas are always larger than the males. No matter what the gender, fleas are at their largest size around 48 hours after feeding.

Engorged Flea
An Engorged Flea – CC Image courtesy of Ryan Eide

Flea eggs are very small and almost invisible to the human eye. They are 0.11 inch long and 0.19 inch wide, so will only be spotted by those with the very best vision and perhaps a magnifying glass. They look rather like tiny grains of rice, colorless or white and semi-transparent.

flea eggs

Once the larvae hatch from the eggs, they appear as very small, white “worm-like” creatures and are visible to the naked eye. They are about 0.07 inch long, but are often not seen as they immediately hide themselves in carpet fibers or cracks in the floor to hide from light. They grow in size to around 0.15 inch, before they become ready to transform into the pupae stage.

3rd Instar Cat Flea Larva
3rd Instar Cat Flea Larva

Flea pupae look a lot like adult fleas within the cocoon. They have the same narrow bodies and mouthparts, however, their legs are not attached to them at the early stage of development. Their bodies start off a pale cream shade, before gradually turning into the brown color of an adult flea. Flea pupae are usually about the same size as an adult flea, but because they have hidden themselves away for this stage, they are very rarely seen by people.

flea pupae
Flea Pupae

How Do Fleas Reproduce?

Female fleas have to mate in order to lay fertilized eggs. Virgin female fleas will still lay eggs, but they will not be viable. Once the females have mated, the eggs not only become viable, but the female will start to produce four times as many eggs as she was previously.

Fleas locate a mate and fornicate while upon their host. Adult fleas generally start to mate around 24 hours after their very first feed upon the host, with the copulation taking around an hour from start to finish.

Fleas are generally anautogenous. This means that they must feed before they can produce eggs. If a flea hasn’t had a blood meal within 24 hours, they will not attempt to mate, because they will not be fertile.

How Many Eggs Do Fleas Lay?

The average female flea will lay between 20-30 eggs every day, although during one study a female flea was recorded laying 46 eggs in one day! Generally, a flea can survive for about a week upon their host, which means female fleas have the potential to lay around 180 eggs during their life. When you consider that this is a single female flea, it becomes easy to see how a flea infestation can rapidly become out of control.

Flea eggs are quite large compared to the body of a female flea. For this reason, they can only lay one egg at a time, with one egg usually being produced per hour on average. At any one time, a female flea could have as many as six eggs in her abdomen ready to be laid.

The amount of eggs laid is directly correlated to the food supply available to the flea. For example, cat fleas prefer to feed upon cat and dog blood. If they are on their preferred host, they will be able to lay 20-30 eggs per day. However, if they are without the preferred host and are merely surviving upon human blood, this will affect their fertility. As a result, they will only be able to lay around three to four eggs per day, which is a huge difference.

Therefore, households without pets will usually have a flea population which is much slower growing, than one with pets.

How Long Do Fleas Live?

Fleas can usually survive for quite a long time upon their host if treatment is put off. In one experiment, cats had their claws removed and had collars placed around their necks to stop them from grooming. After 50 days, 60% of the male fleas and 85% of the female fleas were still alive. Typically, the lifespan of a flea is somewhere between 2-3 months.

The main cause of death for fleas is being consumed by their host when it grooms itself. Fleas will choose to stay permanently upon the host once they have fed, which increases the risk of being eaten during grooming, but also provides protection from the elements.

fleas on cat's stomach
Fleas on a cat’s stomach

A cat will kill more than half of its fleas by grooming, usually within seven days of the fleas taking up residence. This equates to an average of 12 fleas a day, every day. In a particular study, cats were found to have groomed away 38.5% of male and 19.5% of female fleas within 7 days. Over a 21 day period, cats have the ability to kill 90% of their fleas, but of course, they soon return as the life cycle continues.

The fleas which have not been consumed can be dislodged during the grooming process. Sometimes these fleas will be injured and die as a result, but generally, fleas are quite hardy creatures which can survive being kicked off the host’s body. The main risk to dislodged fleas is finding their way back onto the host. They will die from starvation within a few days if there is no access to a blood meal.

A Feeding Flea
A Feeding Flea

Young fleas which have just hatched must have their first feed within one week, otherwise they will die. Adult fleas can survive a little longer without food, but the environment which they are in plays a major role in the length of time they can survive.

Studies have shown that adult fleas can survive for as long as 15 days at 75.2 F and with a humidity of 78%. However, if the humidity and temperature levels dropped to 60% and 72.5 F, they only survived for just over 12 days.

Fleas do very well in environments which are cool and humid. These environments can support starving fleas for as long as 40 days in some studies. One scientific trial kept fleas at 100% humidity and cool air. While these conditions would be rarely found in reality, the fleas in this environment survived without food for 70 days.

If a breeding female is dislodged from the host, she will usually die within a day if she does not find her way to a blood meal. This is because her metabolism will have changed to sustain the production of viable eggs and will require blood to keep her alive.