Where Do Roaches Come From and How Do They Get Into Homes?

By: Cristen Conger  | 
A cockroach on the top of soap dispenser.
Oh the irony. Soap is no roach repellent. See more insect pictures.
Dennie Cody/Getty Images

No one wants to shoulder the blame when it comes to a cockroach infestation at home. Admitting that your house or apartment has roaches is like pinning a scarlet "R" on your chest for all to see. But where do roaches come from, and how can we firmly tell them to take a hike?

Roaches (whether they're American cockroaches, German cockroaches, or another species) can get into the cleanest of living spaces because in most situations, we unknowingly bring them home. One may have burrowed into a paper grocery bag or jumped into your briefcase at work.


Or you could have toted roach eggs into your new homestead without knowing it. Since the critters have nocturnal habits, you may not realize that you've made some six-legged friends before they've added an extra set of branches to the family tree. In this article, we'll find out where roaches come from and how to protect your home from cockroach infestations.

What Brings the Most Common Indoor Roaches to Your Home?

If roaches are house hunting, they can check out your place by crawling through tiny gaps around doors, pipes, and other open spaces. Some adults can grow fairly large, but can shimmy through slits as thin as one-sixteenth of an inch (0.15 centimeters) [source: Ogg et al].

Contrary to popular belief, they aren't simply attracted to messy households, although that will extend their stay. Instead, common roaches that invade homes seek out warmth, moisture and darkness. Pizza left sitting out on the counter is just an added bonus.


Part of the reason they've become such widespread pests is because cockroaches thrive on very little. The insects require three things: water, food and warm shelter. Roaches have lived off the bare essentials with few changes since their creation 320 million years ago [source: Ogg et al]. Even the areas they choose for nesting indoors are minimalistic — cramped spaces in walls, behind picture frames, under sinks, and elsewhere.

Once it hits you that roaches are inside your home, getting to know them is your last concern. On the next page, we'll go over the first steps on how to show any roach infestation the door.



Ways to Get Rid of Roaches

Two cockroaches crawl on a piece of wood
Cockroaches enjoy wood and wood pulp products.
Altrendo Nature/Getty Images

Before you start spraying pesticides on every open surface of your house in an attempt to kill the roaches, you need to strategize. Plotting out an attack on a group of insects may sound borderline crazy, but you'll have more success if you plan ahead.

To do that, let's go back to those three things that roaches need: warm areas, food residue, and water. Taking away those elements is like serving them an eviction notice. A single pesticide will not permanently do the job [source: University of California Statewide Integrated Pest Management].


Setting Up Traps

First, you need to figure out where the bugs have set up camp. If you've noticed them in an isolated area, such as the kitchen sink, that's a decent clue they're hidden away in there. For a more precise indicator, put out strips of roach traps that are coated with a sticky glue to stop them in their tracks.

The heavier trafficked strips should be closest to their nest. You can use this method repeatedly throughout your roach-eradicating mission to check your progress and whether they've changed locales. Also check around for droppings, egg sacs, shed skins, and exoskeletons.

Eliminate Their Food Sources

While you're waiting on your trap results, you've got some cleaning to do. Even if you keep things tidy, you probably haven't covered every spot that serves as a feeding trough for roaches. Items in particular that you should get rid of include:

  • Piled newspapers
  • Cardboard boxes
  • Paper bags
  • General piles of clutter where roaches can hide

Roaches are especially drawn to paper products because they readily absorb a certain pheromone, or chemical attractor, that roaches emit. This aggregation pheromone is like a GPS system, whereby roaches communicate their locations to others and leave a trail for them to find their ways back and forth.

Remove Food Particles and Water

It's also time to give your house, and especially your kitchen (where you store food), an intense bathing. Get any fresh fruits, vegetables, and bread off the counters and into airtight containers. Check through your groceries and secure open bags and boxes. Clean the eyes on the stove, inside the oven, the microwave, and other appliances. Pay attention to grease because even small spots of it are like foie gras for roaches. Sweep or vacuum behind large appliances and remove any food debris at the bottom of dishwashers.

After all of that, you must maintain a high level of cleanliness to eliminate your pest problem. Never leave dirty dishes in the sink, or abandon food on countertops. Routinely sweep after cooking and take out your trash.

Perhaps more than food, roaches seek out watering holes. For that reason, search around for places that could collect water, such as plants, the drip plate under your refrigerator, or condensation around leaky water pipes. Try to keep those areas dry, especially at night when roaches feed.

Place stoppers over your drains and check your faucets to ensure that screens cover their spouts where roaches could crawl in [source: Ogg et al]. Also, place some traps around your plumbing pipes to make sure cockroaches aren't in the vicinity. Now you're ready to pull out the big guns. Learn how on the next page.


Pest Control for Roaches

Once you've taken away the food and water that attracts cockroaches, you're ready to kick them out of their nests. Using the sticky traps, you should have a good idea of where they live. Next, find any cracks or crannies in that area or places that you've seen roaches escape. Fill those gaps with a flexible caulk that prevents roaches from getting back into your living space.

Roach Baits

Roach baits and boric acid are your next line of defense if those previous steps don't reduce the population [source: University of California Statewide Integrated Pest Management]. You can purchase boric acid as a powder and lightly dust it in the cracks you can't seal off with caulk, such as under sinks and appliances and behind cabinets.


Roach baits in gel form also work well in those tricky spaces, luring the insects to them and poisoning them. Don't apply near food preparation areas and be sure to store out of reach of children and pets.


The Environmental Protection Agency only urges consumers to up the ante to pesticides as a last resort [source: EPA]. If you make that move, there's a distinction you should understand when shopping. Many of the ready-made sprays grocery stores sell are contact repellents. That means you have to actually strike a roach with the liquid to kill them.

Repellents in general also won't cure your problem forever. They simply keep roaches at bay, potentially moving them to another area of the house or apartment, depending on where you live. For killing the insects, stomach poisons, such as the commonly-used boric acid or bait gels, may be more effective [source: Ogg et al].

There are many other pesticide categories companies offer, including:

  • Desiccants: substances that dry out roaches to kill them
  • Insect growth regulators: chemicals that inhibit roaches' growth and reproduction
  • Ready-to-use spray: premade sprays, which are often repellents
  • Emulsifiable concentrates: sort of like the frozen orange juice of pesticides. A concentrate to which you add water.
  • Aerosols: most work as contact repellents
  • Foggers: release a mist of pesticide that fills the air. You cannot be home during fogger applications.


The Right Approach Will Oust Your Indoor Pests

Knowing where and how to apply your poisons also influences your results. For instance, thin layers of boric acid powder are more effective than thicker ones. After putting on your protective eyewear, breathing mask and gloves, you want to go back to those cracks and crevices we've been talking about. Apply your pesticides in those spaces that you weren't able to seal off with the caulk, taking care to not damage any appliances.

If, after all this effort, you flip on the switch in your kitchen and behold the skittering of roaches, don't lose hope. Many pesticides take at least a week to produce visible results. Packaging should also contain helpful information as well. Just remember that doing one thing alone will not kick roaches to the curb. When you're up against insects that outlasted dinosaurs, you'll need a multi-tiered battle plan.


For related information on roaches and pesticides, visit the links below.

Lots More Information

Related HowStuffWorks Articles

More Great Links

  • "Cockroaches." University of California Statewide Integrated Pest Management. June 2007. (July 2, 2008) http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7467.html#MANAGEMENT
  • "Get Rid of Cockroaches." New York Department of Health. Updated October 2005. (July 2, 2008) https://www.health.ny.gov/publications/3202/
  • "Get Rid of Roaches!" Environmental Protection Agency. February 2004. (July 2, 2008) https://nepis.epa.gov/Exe/ZyPDF.cgi/P100NB96.PDF?Dockey=P100NB96.PDF
  • Kunkel, Joe. "Cockroach FAQs." University of Massachusetts. Updated June 10, 2008. (July 2, 2008) http://www.bio.umass.edu/biology/kunkel/cockroach_faq.html
  • Ogg, Barbara; Ogg, Clyde and Ferraro, Dennis. "Cockroach Control Manual." University of Nebraska. July 2006. (July 2, 2008) https://lancaster.unl.edu/pest/roach/cockroach%20manual.pdf