Are Fleas Attracted To Light Or Heat? (Ways To Keep Them Away)

Adult female fleas cannot lay eggs until they feed on a blood meal. A hungry flea is in constant search of an animal or human host. Once a human walks by, the flea will readily jump onto the new host and bite the area around the ankles. 

An adult female flea will then mate and begin laying eggs. The eggs will take anywhere between 1-12 days to hatch, depending on the environmental conditions. They will only hatch when the temperature and humidity are ideal for them. 

If it's cold and dry, flea eggs usually take much longer to hatch. But when the temperatures get warmer, and humidity levels start rising, the eggs will hatch much faster! 

The answer to the question 'are fleas attracted to light or heat?' is not as straightforward as many would wish. That's because whether or not fleas are attracted to light or heat primarily depends on what stage in their life cycle the pest is in. 

For instance, the larvae that emerge from a flea egg are blind and avoid contact with light. Comparably, once a new adult flea emerges from its cocoon, it must feed on a blood meal within 7 days, or else it will die of starvation. The adult flea depends on factors like visual and thermal stimuli (light&heat) to detect a suitable host.  

So, the short answer is yes, fleas are attracted to light and heat more than other factors like host odor, physical contact, and movement. Sounds surprising, right? To help you understand the relationship between light, heat, and fleas, we'll need first to give you a few facts about the flea life cycle. 

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The Flea Life Cycle 

A flea typically goes through four stages in its life cycle, including the egg, larvae, pupae, and adult. A complete flea life cycle can last anywhere between a few weeks and many months, depending on the environmental conditions (temperature and humidity). The ideal conditions for fleas to thrive are between 70°F-85°F and 70% humidity.


The life cycle begins when an adult female flea lays an egg soon after mating. As stated earlier, fleas cannot lay eggs unless they have had a blood meal from a suitable host.

Flea eggs are quite small and almost microscopic as they typically measure about 0.5 millimeters in length and are only half as wide. The eggs are loose with an oval shape and a softshell with an off-white color.

Fleas usually lay their eggs in your pet's fur, often in bunches of about 8-20. A single adult female flea can lay up to 40 eggs in a single day! Depending on how long your pet's fur is, flea eggs can dislodge and fall off within a few days. This allows them to be distributed in your pet activity areas and places where the pet spends most of its time.

Flea eggs can hatch within 1-12 days, depending on environmental conditions. When the temperatures and humidity are optimal, the eggs will hatch, and the next life stage (larvae) begins.


The flea larvae are usually blind and tend to keep away from light by all means. They feed on predigested blood, often referred to as flea dirt. This dirt is actually the feces excreted by a flea, usually as it sucks blood from its host.

Flea larvae typically look like tiny worms measuring about 1/4 inch in length with a whitish, almost transparent, and legless body. In optimal conditions, the larvae will form cocoons in only about 5-20 days after they've hatched from their eggs. The larvae soon develops into the next flea life stage (pupae).

Flea larvae typically look like tiny worms measuring about 1/4 inch in length with a whitish, almost transparent, and legless body. In optimal conditions, the larvae will form cocoons in only about 5-20 days after they've hatched from their eggs. The larvae soon develops into the next flea life stage (pupae).


The pupae of a flea also called the cocoon, is the last stage before the flea develops into a fully mature adult. Generally, a cocoon is a silky casing spun by the flea larvae to protect the pupae for some time before it develops into an adult. 

If the environmental conditions in your house are not ideal for emergence, the pupae will remain protected within the cocoon for months, and in worst cases, years!

It's quite difficult for homeowners to get rid of flea pupae. That's because the sticky cocoon allows them to burrow deep into carpets, making it hard to remove them with quick vacuuming or sweeping. In addition, the cocoon also protects the developing pupae from chemical treatments.

Note that even when fully developed, an adult flea cannot emerge from the cacoon unless a potential host is present. They will detect the presence of a host by body heat, vibrations, and even increased levels of carbon dioxide. The adult fleas will be triggered to emerge from their cocoons to feed on a host when your pet walks by and as people move into the house.


Once it detects a potential host, the adult flea will quickly emerge from its cocoon to take a blood meal. It begins feeding within a few hours, and soon after that meal, the adult will mate and start laying eggs in a few days. 

A newly emerged adult flea is quite small. It usually has a flat-bodied appearance with a dark color. After a couple of blood meals, the flea grows much bigger, and its color becomes lighter. Their long hind legs are quite powerful, allowing them to jump up to 16 inches horizontally and 8 inches vertically in pursuit of a human or animal host.

Most of an adult flea's time is spent feeding on a host, mating, and laying eggs. They can live anywhere between a few weeks to several months in optimal conditions.


Are Fleas Attracted To Light? 

As noted above, flea larvae avoid being out in the light and instead prefer spending their time hidden deep in a host's fur, on carpet, or grass. Because flea larvae feed on the flea dirt passed by an adult, they do not need to search for a host.

However, once it develops into the adult stage, the flea comes to the surface in search of a host. Adult fleas are attracted to light, but not in the way that you imagine. Unlike other insects that fly toward a source of light, adult fleas don't have wings and won't fly or jump toward a lamp or any light source. Fleas respond completely differently to light. 

Numerous studies found that newly emerged fleas from a cocoon are sensitive to light. More specifically, 93% of the fleas used in the study moved from a dark place to a lighter one in only 40 minutes.

Interestingly, the researchers found that a flea's attraction to light is greatly increased when the light source is turned off fast and then back on immediately. This speedy interruption is likened to a shadow cast by a potential host passing by, triggering the adult flea to jump toward the perceived food source.

So, while fleas use light to help them detect a suitable host, they are not attracted to light per se. Instead, their simple eyes can see changes in light intensity so that they are able to detect shadows cast by a potential passing host.

What Light Color Do Fleas Attract To? 

Fleas are not attracted to all light colors. Studies found that fleas are more attracted to green-yellow lights than the standard light. That explains why flea traps often use a green-yellow filter for the best results. Other light colors like blue and green also have a similar effect on fleas as standard lights, which attract significantly fewer fleas than green-yellow lights. 

The studies also observed that flea traps that use intermittent light consistently attract and trap an increased number of fleas compared to the traps using a constant light source. The interruption in light creates a shadow similar to the one created by a potential host passing by. This distraction triggers the flea to jump and follow the 'host.'

If you want to use a lamp flea trap, you should consider using one with intermittent light as it provides 5 times better results than the one using continuous light.


Are Fleas Attracted To Heat?

Fleas, like any other organisms, respond to heat, a process known as thermotaxis. Fleas tend to move towards a source of heat (positive thermotaxis or thermophilic). Thermophilic behavior is rarely exhibited by other organisms.

Flea's sensory organs can detect the heat produced by a living creature. The heat enables fleas to distinguish between alive and dead objects. 

Flea antennae are very useful in detecting heat from a potential host. Most people are surprised to learn that fleas have two antennae.

That's quite understandable, seeing as fleas typically have antennae fossae, which is a different type of antennae from other insects. Fleas' antennae are located in a depression or cavity located behind their eyes and can only be observed with a microscope as they are extremely small.

Though microscopic, these antennae have a highly sensitive response. They are very powerful sensory organs that detect vibration, heat, smell, humidity, and touch!

Fleas are attracted to heat from a potential host. The heat of a passing animal or human triggers adult fleas to emerge from their cocoons and jump toward to heat source. Note that heat alone will not stimulate an adult flea to emerge from its cocoon. Other factors like a change in light intensity and carbon dioxide are required to trigger the adult to emerge.

The Best Way To Keep Fleas Away 

So far, it's evident that fleas are attracted to light and heat. These filthy pests can infect people and pets with bacteria and germs that cause serious diseases like murine typhus and bubonic plague. Hence, it's important that homeowners learn the best way to get rid of fleas naturally and effectively: 

  • Lemon spray: Fleases have a very strong sense of smell, and they literary dislike the smell exuded by lemon spray. Slice a lemon and add it to a small amount of water. Heat the mixture and allow it to boil, then leave it to cool overnight. Pour the solution into a spray bottle the following morning and spray all the flea-infested areas. 
  • Herbal Flea Spray: You can easily find a nontoxic flea spray at the grocery store. Spray the treatment as instructed in the labeling while paying keen attention to upholstered furniture, carpet, and rugs. For the best results, spray the treatment after vacuuming thoroughly. 
  • Baking Soda: Baking soda works by dehydrating and killing flea larvae and their eggs, thereby breaking the flea life cycle. Use baking on upholstered furniture and carpets after vacuuming. Work the powder into the fabric using a soft bristle brush. Vacuum after some time and empty the dust bag into the trash bin outdoors. 
  • Salt: Salt can be used in the same way as baking soda to dehydrate and kill fleas. This dehydration agent will suck moisture out of the fleas' environment, causing both the larvae and adults to dry out and die. Should the salt come in contact with the adult fleas, larvae, and their eggs, it takes out all the moisture, eventually killing them. Ensure to apply a generous amount of salt all over your house and leave it for 24-48 hours before vacuuming. 
  • Professional Pest Control Services: Perhaps you're dealing with a full-blown and massive flea infestation? The only way to get effective control and protection results is by seeking help from a professional pest controller. The experts will thoroughly inspect your entire home to determine the cause of the infestation and customize an effective treatment plan for your home. 

Related resources:

How To Get Rid Of Fleas In Blankets


  1. Very nice article! Thank ypu for the information. I have 3 days ago observed some red itchy spots on my skin. Yesterdsy I found 1 flea on my leg, so the I knew who is biting me. Interestingly I dont own pets, so i think they came from my neighbors pets or from outside .

  2. Hi there,

    Thank you for taking the time to read my article and for your kind words. I'm sorry to hear that you're dealing with a flea issue, especially since you don't own any pets. Fleas can indeed come from neighboring pets, or from outdoor environments, especially if there are animals like squirrels or raccoons nearby.

    Given what you've shared, it sounds like the suggestions in the "The Best Way To Keep Fleas Away" section could be helpful for your situation. Remember to be thorough and persistent with these methods, as fleas can be quite tenacious. If your efforts don't yield results and the problem persists, I would recommend considering a professional pest control service. I hope this situation resolves soon for you!

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