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Why Do Roaches Run When You Turn On the Light?

Top View Dead Cockroach

Imagine staying alone in your room at night and you hear unusual crawling noises behind your cabinet. You flick the light on and see a roach scattered around the area. Now what?

Roaches are nocturnal animals. This means they are used to spending time in dark and warm places to look for food and thrive. And it also explains why you see them scattered and are quick to escape when you turn on the lights.


Because being nocturnal is part of the roaches’ nature, you will commonly see them run or try to escape when you turn the lights on.

This does not mean they are afraid of the brightness. Instead, they see the light as a representation that humans have seen them. It’s all thanks to evolution.

Roaches learned to start running and hiding when they see light.

But did you know that an Asian Cockroach is attracted to light? So the next time you see a roach that does not avoid the light, it might be an Asian Cockroach.

This guide talks about the behavior of roaches when exposed to light and the signs that tell your house is experiencing a roach infestation. Plus, we’ll give you tips on how to keep them away at night.

Why Roaches Run Away From Light

Brown Cockroach Closep Crawling

Even though roaches have tiny brains, they are smart enough to know that light means danger.

Technically, these pests are not afraid of the light, but they stay away from it because it means they are running close to human interaction. And what happens when humans see them? Death.

Roaches scurry away from light also because they equate brightness with negative consequences. These pests believe that when lights are turned off, humans have already seen them.

You often see them running faster to reach darker places or gaps behind your furniture. This is because evolution has taught them that they should run fast to stay alive.

When you switch the lights on, roaches are not afraid of the brightness. Instead, they are afraid of you.

Keeping Lights On

Your next question would probably be, “Should I keep the lights on to prevent roaches from coming out?”

The answer is yes and no. Because roaches believe that having lights on means you’re ready to catch them, they’ll do their best to stay hidden in dark crevices and small corners.

When lights are turned on, it’s also easier for other predators to see and eat them. And because roaches are afraid to get killed, they will try to look for dark places where they can hide.

But when it takes too long before lights are switched off, roaches may grow tired of staying in a particularly dark place. This is especially when they have sought out all possible means of food sources.

When this happens, roaches have no option but to crawl away from the dark corner despite the bright light. What they can do is crawl and search for food faster so they can hide in the next dark area they see.

Why Roaches Prefer the Dark

Closeup Animal Red Cockroach Night

We know we’ve said it before. Roaches prefer the dark not because they are afraid of light and brightness. Instead, these pests prefer to come out when it’s dark because they believe there are fewer predators at night.

It also means less human interaction and a lower chance of getting caught and killed. If there are fewer predators and humans, roaches feel safer going out.

Moreover, at night, there are fewer instances that the roaches’ food source gets removed by humans. This means it’s easier for these pests to look for more food and survive.

How Roaches Can See in the Dark

Roaches can see even in pitch darkness because of the light-sensing cells in their eyes. These cells can pool a few light signals over time in a given space, which allows them to see in the dark.

Researchers who tried to record the individual light-sensing cells revealed that each photoreceptor could receive a single photon every ten seconds. This is equivalent to light levels on a moonless night.

Signs Your House Is Experiencing Roach Infestation at Night

Two Cockroach Egg Lay

You see a roach when the lights are switched on. So yes, it’s a probable sign that your room might be experiencing a roach infestation. But aside from this obvious sign, other ways could tell roaches are invading your house.

Some of these signs include the following:

  1. There is an unusual smell.
  2. Dropping from roaches that resemble coffee grounds.
  3. Egg casings from roaches.
  4. Shed skins from cockroaches.

The most common sites of roach infestation include kitchens, bathrooms, basements, attics, drainage systems, and laundry rooms. These areas are usually close to humidity and moisture, which roaches prefer.

Keeping Roaches Away at Night

Cockroach Floor Leftovers On Plate

Because it’s challenging to catch roaches at night, especially when lights are not turned on, you can perform preventive measures to help keep them away when you sleep.

Here are our top recommendations:

  1. Always make sure food containers are tightly sealed.
  2. All utensils should be cleaned and dried before placing them in your cabinets or cupboards.
  3. Waste bins should be regularly emptied outside.
  4. All holes, gaps, and cracks should always be sealed.
  5. Vacuum and mop your floors to ensure no stains or food crumbs are left behind.

Roaches Prefer the Dark

Roaches run away at the sight of light mainly because they equate brightness with predators and humans. They believe they won’t find a way to escape once you see them. Hence, they die.

Roaches prefer dark places because they can thrive better and survive. They can easily look for more food and feed themselves without being disturbed by other predators.

Plus, dark places meant they could eat anything they found. Roaches also have no problems seeing in the dark, thanks to the photoreceptors in their eye cells.

The next time you suspect a roach infestation, preventive measures should do the trick. Seal cracks and holes, and always clean all surfaces.

Plus, don’t forget that these pests also prefer waste bins, so empty them regularly.

Frequently Asked Questions

Can Roaches Run When They See Humans?

The eyes of cockroaches are made up of compound lenses that allow these creatures to see you. And if they can’t see you, they can detect your presence because of the tiny hairs on their bodies.

These tiny hairs allow these pests to detect or sense any movement within their vicinity.

Why Do Roaches Invade Your House More After a Heavy Rain?

The main reason roaches tend to enter human houses after a heavy drain is to avoid drowning. Flooding happens when sewage systems are filled with rainwater, and roaches can be flushed out.

As a way to escape, these pests will try to enter tiny holes and gaps that lead to houses.

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