When are Cockroaches Most Active?


Cockroaches are creatures of the night. That’s when they come out of their dark, dank hiding places to forage for food and to mate. That’s when you are most likely to encounter them, on your foray to the refrigerator for a late-night snack, or when you get up before sunrise to get an early start on your day.
If you don’t travel through cockroach habitat at night, you will probably only know you have roaches by their calling card: Cockroaches aren’t house trained. Smaller roaches leave tiny pellets of fecal matter, while larger roaches leave an impression of, well, diarrhea. And since cockroaches feed on their own waste, you will see more and more evidence of roaches every day unless you take the necessary steps to get them under control.

Cockroaches have a circadian rhythm opposite humans

Most species of roaches that infest houses and apartments shun daytime activity. As Dr. Terry L. Page of Vanderbilt University in the USA puts it, cockroaches are morons in the morning and geniuses at night. Roaches have a circadian rhythm that favors night-time activity. Their eyes focus better at night and their vision becomes relatively blurry during the day. Their sense of smell (in their antennae) does a much better job of finding food and identifying poisons at night than in the day. When roaches find a food source at night, they will remember it for the rest of their very short lives. If they stumble across food — or poison, or a baited trap — during the day, they won’t pay particular attention to it.
During the day, the preferred activity of a roach is sheltering in place. They flatten themselves to fit through tiny cracks and crevices to find shelter from their predators near leaky pipes, or behind furniture, or underneath stoves, refrigerators, and pet food bowls. But careful attention to cleanliness can disrupt the cockroaches’ night-time routine.
Roaches find their harborages, their hiding places, with the help of pheromones. If you have ever had a problem with roaches, you may have noticed a distinctive musky odor that is a little like the odor of cat pee and poop. Roaches use that scent to find their way to other roaches in a safe harbor. If you get rid of the odor, you deprive the roaches of a way to find other roaches with which to shelter and mate.

Use the circadian rhythm of roaches against them

So how do you get rid of roach pheromones? The simple answer is to clean, clean, clean. Pull out the stove, mop away any roach droppings, and replace roach smell with the odor of household cleaner. Empty out cabinets and pull up old lining paper, Spray the bare shelf with a nontoxic, natural roach repellent.

Not all “natural” insecticides are non-toxic. In the US, look for products that are labelled as “EPA exempt” and “FDA approved for use around food.” In the UK, the label will be “Eco-Friendly.”

Never leave food scraps uncovered. Use trash receptacles with a roach-proof lid. Put away pet food bowls at night, especially if you feed your pets products with lots of grains and fillers.
And consider shining a light on your roach problem.  Cockroaches are active both day and night, but they are vigilant, actively protecting themselves from predators, more sensitive to the taste of poisons, and more alert to traps, in the dark. Their vigilance falls off when the lights come on. Putting lights on a timer so that roaches are periodically signalled throughout the night that it’s time for a nap  reduces cockroach activity.

Cockroaches can’t see red light, but they are very sensitive to blue light. Humans are sensitive to blue light, too, so you may want to keep the door to the area you keep lit at night kept shut so it doesn’t interfere with your sleep.

In addition to turning on lights, every night you need to follow a kitchen cleaning routine like this:

  • Leave absolutely no dirty dishes, pots, or pans in the sink, on the counter, or on the stove. Everything has to be washed or locked in the dishwasher.
  • Don’t leave even a tiny speck of food in the sink. Baby cockroaches are the size of a particle of dust.  They can feed on food particles you can’t even see.
  • Cover pet food bowls, or put them away. Don’t leave roaches an all-you-can-eat buffet of pet food.
  • Turn off faucets completely. Roaches are attracted to water as well as food.
  • Either take the trash out, or make sure everything is in a roach-proof receptacle.
  • Deodorize. Roaches are confused by household cleaner and aromatherapy scents. If it smells good to you, it smells bad to roaches.

And when you notice that distinctive musky, roach-y odor ,day or night,  it is time for a thorough cleaning. Mop under the stove and under the refrigerator. Wipe down cabinets and under the sink with disinfectant cleanser. When the scent of your home is attractive to you, it repels roaches day and night.


Simon Mann is a "handy man" to have around the house. Although he was a trained carpenter he went on to become a VP of a construction company. Any pest or DIY problem you may have, he always seems to come up with the right solution.

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