You’ve seen a cockroach before but not one like this—not one carrying a strange protrusion like a brown bean or a tiny purse behind it. That “purse” is an egg sac carrying precious cargo: dozens of roach eggs!
And you’ve discovered a pregnant cockroach.
That’s a truly rare encounter, one that might inspire awe if it didn’t trigger such a terrifying thought: all of those baby roaches are about to invade your house!
We’re going to show you what to do when you find a pregnant roach, how to deal with its offspring once they hatch, and how to keep all roaches, including pregnant ones, out of your home for good.
Let’s dive in!
Overview of the Cockroach Life Cycle
We’ll use the German cockroach, arguably the worst cockroach pest in the United States, as our life cycle “lab rat.”
In the right conditions, a roach could sprint through these stages in just 100 days.7
The Pregnant Cockroach and Her Eggs
A female cockroach can begin to reproduce as soon as she reaches adulthood. The roach is oviparous, which means her offspring grows outside of her body in eggs. In the case of cockroaches, eggs develop in an egg sac, called an ootheca.
The oothecae is a tiny, purse-or bean-shaped capsule that contains as many as fifty eggs. The larger the egg case, the more eggs it contains.
A female roach produces one egg sac at a time but could tally ten or more over her lifetime.
You’ll know you’ve found a pregnant roach if it appears to have a pill-shaped protrusion sticking out like a fat, ribbed tail. This extends further as more eggs develop inside it.
The “pregnant” female carries her egg case for about 1 month until the eggs are ready to hatch. She might continue to carry it; otherwise, she’ll deposit it in a safe and hidden location, usually deep in a wall crevice, under a heavy appliance or deep in a cluttered cardboard box.
Within a day or two—provided it stays hidden and moist—the eggs will hatch.2
From the eggs come many tiny cockroach nymphs. Cockroaches have hard exoskeletons that don’t change in size. As the baby roaches grow, they need more room to breathe… literally.
To molt, a nymph inhales until it bursts out of its old exoskeleton. Then it grows a newer, larger one.
Just after molting, roach nymphs appear white until their new outer covering forms.
A German cockroach nymph reaches adulthood in about 2 months.7
As soon as a cockroach “gets its wings” (if it’s a species with wings, that is) and reaches adulthood, it’s ready to start reproducing.
In lab studies, about 85% of nymphs survived to adulthood.7 Just 3 days after their final molt, these bugs are already mating!
A female can often reproduce for her entire life from just a single mating.7
Adult German roaches live about six months, during which time one female might produce anywhere from 400 to over 1,000 roaches!
Cockroach Egg and Nymph Development by Species
|Species||How long till egg hatches||No. of Nymphs per hatching||How long till adulthood|
|German||30 days||40–50||2 months|
|Oriental||60 days||15–20||1 year|
|American||40–50 days||15||6 months to 1 year|
|Smokybrown||45 days||20||320 days|
|Brown-banded||70 days||15||160 days|
What Does It Mean to Find a Pregnant Roach?
Bad news: finding a pregnant roach means if you don’t already have an infestation, you’re about to.
How fast does a cockroach infestation grow?
Think about it.
One female German roach produces 40 eggs. Let’s say it’s an even split between males and females. A month later, the 20 females each produce 40 offspring. If that pattern continued, in just 4 months you could have 16,000 roaches running riot in your home!
It depends on the species, the environment and a few other factors but it’s not hard to imagine one pregnant roach becoming thousands, if not ten-thousands, within 6 months. Various studies have shown that German roaches can achieve a 20x in just 3 months.7
Already, the exact number of zeroes hardly matters; it’s too many cockroaches and a huge safety risk.
What to Expect: Seeing and Smelling
You’ll see plenty of signs as a roach population multiplies that quickly.
- First, you’ll start to see droppings in more and more places. Roaches spend most of their time hiding but as the population grows, more of them will be forced out into the open. Hence, the clusters of tiny black specks you’ll see popping up in new places every week.
- Second, you’ll see more and more roaches, living and dead. Maybe you’ve gotten used to spotting a roach or two in the kitchen every few days. If you do nothing, that could become a daily encounter with half a dozen roaches or more. Eventually, they’ll find their way into your appliances, your outlets, your floors and walls, your closets and your drains.
- Third, there’s a chance you’ll start finding egg sacs in cardboard boxes in the attic and beneath your favorite furniture.
- You might also start to smell the bugs. Cockroaches in large numbers produce a stale, musty odor that will become noticeable in heavily-infested rooms.
Act Fast: How to Stop a Roach Infestation
We know all of this sounds scary but you have the power to stop the spread of roaches starting today!
Let’s break down exactly what you should do when you find a pregnant roach to ensure that’s the last one you’ll have to deal with!
Effective Roach-Killing Tools
You’ve got a number of cutting-edge roach control tools at your disposal, from good old fashioned sticky traps to advanced gel bait formulas.
- Start with traps, positioning glue traps or roach motels in high-risk areas like the kitchen and bathroom. You can trap roaches along baseboards and behind appliances, too.
- Learn all about choosing and setting traps in our guide.
- Move on to gel bait, applying pea-sized drops of the gel in cabinets, beneath appliances, behind shelves and in cracks and crevices. Make it easy for the roaches to take the bait, which they’ll unwittingly share with other roaches after it kills them.
- Learn all about choosing and using roach bait in our guide.
- Shore up your defenses with insecticidal dust, spreading a fine layer of CimeXa or boric acid on shelves, floors and other surfaces where roaches frequently travel. You can even dust in wall cavities and floor voids to kill cockroaches where they’re hiding.
- Learn all about applying roach-killing dust in our guide.
- Finally, the backbone of it all: sanitation and exclusion. Keep things clean and closed up to prevent roaches from finding food, water or places to hide!
Prevent More Baby Roaches with an IGR
Ready for the secret weapon that’ll take your roach elimination plan to the next level?
It’s called an IGR and it stands for Insect Growth Regulator.
What does it do? It throws a big ol’ wrench into the cockroach baby factory!
An IGR prevents cockroach nymphs from reaching adulthood. By now, you can probably guess what that means for the colony. No adults means no new babies and no new babies means no future adults.
An IGR spray travels through the air and gets absorbed by the roach’s outer shells. It won’t kill the young roaches it reaches but it’ll render them slow, weak and not likely to survive long in the harsh world you’ve created through sanitation and exclusion.
More importantly, it’ll take care of the hidden threat: the hundreds or thousands of hidden eggs about to hatch. The IGR makes sure these weakened roaches are the last wave by cutting off their development before they can grow up into thousands of egg-laying adults.
Spray the IGR in any area where you’ve seen roach activity or suspect they’re hiding to freeze the colony’s growth.
With this plan of attack, you can deal with anything from one pregnant roach to thousands of the pesky pests roaming around your house.
Now, get answers to a few common questions about pregnant roaches.
A pregnant cockroach is a sign of the worst—an infestation that’s primed to explode if it hasn’t already. You’ve made a rare and fascinating discovery but inside your home it spells nothing but trouble.
Find a pregnant roach and it’s time to act fast. Set your traps, choose your bait and spray an IGR to hit the colony from all angles.
You’ve got this!
Frequently Asked Questions
Lots of people wonder if squishing a pregnant roach will just release all of the baby cockroaches she’s carrying.
Cockroaches are tough to squish. If you crush it but don’t kill it, it’ll just stroll away and hide its eggs per normal.
Even if you do kill the roach, the egg case might survive and hatch just a few days later, spawning a much bigger problem than that one roach.
Make sure you dispose of the dead roach and its egg case outside, in a sturdy bag as far from your house as possible.
Most cockroaches aren’t great fliers to begin with. A big, awkward egg sac is nothing more than added weight throwing a cockroach off-balance as it tries to lift off.
So yes—a pregnant roach can fly, but it won’t fly far and it won’t make the trip with much grace. Call it a gliding jump.
Beetle mimic cockroaches give live birth to their offspring, making them one of the only insects in the world to do so.
These aren’t household pests but they are fascinating bugs to scientists, who are studying them to try to learn more about mammalian pregnancy, including how stress during pregnancy affects the development of the embryos.1
A few other roach species are ovoviviparous—their young grow inside the mother’s body. These also give live birth.2
Don’t worry, we’re not about to give you the talk.
Cockroaches don’t technically get pregnant because most species (see above) don’t give birth to live young. But when they do get “pregnant”, they form the egg sac that will hold their eggs until they hatch.
Some species only mate once; they’ll keep reproducing from that first mating for the rest of their lives.
That’s a big no. A cockroach can continue to reproduce as long as it keeps on living. That’s why one female can be responsible for hundreds of offspring and why it’s so important to use an IGR and the other roach control tools we’ve discussed to kill these bugs as quickly as possible.
- Fuller, Dawn (2016) Study of a pregnant cockroach paves a new direction in genetics research. University of Cincinnati. Retrieved from https://www.sciencedaily.com/releases/2016/01/160105133257.htm
- Wilson, Tracy V. The Cockroach Life Cycle and Behavior. HowStuffWorks. Retrieved from https://animals.howstuffworks.com/insects/cockroach2.htm
- Vector Control – Methods for Use by Individuals and Communities (1997) WHO. Retrieved from https://www.who.int/docstore/water_sanitation_health/vectcontrol/
- Smokybrown Cockroach. Oklahoma State University Entomology & Plant Pathology. Retrieved from http://entoplp.okstate.edu/ddd/insects/smokybrownroach.htm
- Oriental Cockroach. Oklahoma State University Entomology & Plant Pathology. Retrieved from http://entoplp.okstate.edu/ddd/insects/orientalbrownroach.htm
- Newbern, Elizabeth (2016) Mom Genes: This Cockroach Species’ Live Births Are in Its DNA. Live Science. Retrieved from https://www.livescience.com/53480-cockroach-pregnancy-unraveled.html
- Ross, Mary H. and Donald E. Mullins (1995) Understanding and Controlling German Cockroaches. Oxford University Press.