Cockroach eggs are not a happy discovery in any home. They mean that roaches are nearby, that they’re breeding, and that they’ll soon multiply.
If you’ve found what you suspect to be a cockroach egg, you’ll want to identify it, assess how bad the problem is, then quickly remedy the infestation if it exists.
Let’s begin with the basics:
Do cockroaches lay eggs? Yes and no. Females don’t actually lay individual eggs. They lay an egg case or sack called an ootheca which contains up to 40 eggs. The ootheca is made of a hard leathery material that protects the eggs inside from both predators and insecticides.
Cockroach eggs as you’ll learn, are a formidable opponent in the battle to reclaim your home.
What Do the Eggs (or Ootheca) Look Like?
What do cockroach eggs look like? Cockroach eggs look like small tan, brown or black capsules shaped something like a pill or a purse.
German and American cockroach eggs are approximately 1/3-inch (8 mm) long, while those of the Oriental and SmokyBrown cockroaches are slightly longer, reaching lengths of almost ½ inch (12 mm). Brown-banded cockroaches have smaller egg sacks less than ¼ inch (5 mm).
Roach eggs have a small ridge called a keel running down their length. This is a weak point in the case where nymphs emerge. When it’s time to leave the egg case, hatched nymphs swallow air to make themselves bigger. This causes the egg case to expand and break open along the keel, allowing the nymphs to escape.
When empty, a cockroach egg looks much like one that is full because the keel closes again after the nymphs are gone.
Where to Find Them
Where do cockroaches lay eggs? It depends to some degree on the type of cockroach.
- German cockroaches tend not to release their eggs until just before they hatch, usually about 24 hours. German cockroach eggs sometimes hatch while still attached to the female’s body.
- The American cockroach lays egg cases near food sources and will sometimes adhere them to a surface using saliva.
- Oriental cockroaches deposit eggs in warm, covered areas near food.
- Smoky brown cockroach females tend to hide their eggs in humid crevices (for example, under rocks or in piles of wood or other debris).
- Brown-banded cockroach eggs can be found attached to rough surfaces (e.g., cardboard or sand). If an area is heavily infested, they may appear in clusters.
Your best bet for finding roach eggs is to look near things that adult cockroaches like, such as food, water, and cardboard. Check for them in kitchens where there is plenty of food and water. And bathrooms where drips and condensation make water easy to find.
Inside The Oothecae
How many eggs does a cockroach lay altogether? Oothecae hold between 14 and 48 eggs, arranged in two equal rows, depending on the species. The egg cases of most cockroach species contain between 14 and 16 eggs, while the smoky brown cockroach produces 20 eggs and the German cockroach lays between 30 and 48 eggs1,8,9,12.
Inside The Eggs Themselves
How many roaches in an egg? Each individual egg within an ootheca contains a single developing cockroach nymph. German cockroach eggs for example, can produce as many as 48 baby cockroaches1. Even though they don’t live very long (between 160 and 450 days, depending on species), they can leave behind a lot of offspring. The German and Oriental cockroaches can produce as many as 8 egg cases over a lifetime, while the American cockroach lays up to 10, and the brown-banded cockroach produces around 133,10.
Is There a Queen?
Is there a queen roach? Cockroaches are not truly social insects (like honey bees or termites). As such, they do not have a queen. However, they are considered ‘gregarious’ and tend to congregate during rest times (generally the daytime). Depending on the size of their refuge, groups can number in the millions13.
What does a roach nest look like? Because they are only weakly social, cockroaches don’t produce nests like some other insect species14. However, resting groups return to the same refuge site day after day13, so you can expect this area to be covered in roach feces, shed skin, and perhaps some egg cases1.
Cockroach eggs aren’t the only concern, of course. You’ll want to know where the adult roaches are too. How do you find cockroaches? If you know what they like, it’s actually pretty easy. Cockroaches prefer warm, humid, dark, enclosed spaces and German cockroaches, in particular, rarely venture farther than 10 feet from a food source. Kitchens and bathrooms are favorites1,14. Pipes are great cockroach hiding spots. They may also be found in furniture, cardboard boxes, closets, cabinets, cupboards, drawers, shelves, within or behind appliances, behind or beneath baseboards and trim, and inside light fixtures or electronic devices. However, they may also be found high up and out in the open on ceilings, though you’re likely only to see them out and about at night15,16.
To find them, inspect your home for signs of cockroach infestation, including fecal pellets1 or staining, egg cases, and shed skins1,17. Feces themselves look like black pepper14 and can stain surfaces brown17. Also keep an eye out for food that is being consumed overnight1. A small population may not leave much evidence of missing food, but a large infestation can eat a lot.
If you happen to spot a cockroach scurrying across the floor, see if you can follow it. If it’s not out foraging, it may lead you back to its friends.
Follow your nose. Cockroaches produce a musty, sour, oily smell that is fairly distinctive17,18.
If you’re still not sure, a great way to assess your cockroach situation is to set sticky traps1. Their resting areas are likely near the traps that catch the most cockroaches. Sticky traps will also help you monitor the effectiveness of your management plan. If it’s working, you will catch fewer and fewer roaches as time goes on.
What Kills The Entire Nest?
What kills roaches and their eggs? Let’s look at roaches first.
When you use pesticides for roach control, both choice of chemical and placement are key. Neither the right chemical in the wrong place or the wrong chemical in the right place will kill very many roaches. Use the information you glean from your inspections to choose the best areas for insecticide application.
In general, baits are best for controlling cockroach populations. But a best practice is to switch the types of treatments at regular intervals. Cockroaches can learn to avoid baits and/or develop resistance after prolonged exposure1.
A Closer Look At Insecticides
Some common types of insecticides for use on adult cockroaches are dusts (either synthetic insecticides or natural products like boric acid or diatomaceous earth), liquids (including sprays), and gels for use in or as baits. When using dusts, apply only a thin layer along baseboards and in cracks and crevices. Cockroaches will avoid large piles as they are difficult for them to walk through. Liquids should also be applied thinly behind furniture and appliances and near water sources1,3. Don’t apply liquids on walls, open floors, or countertops. Not only do cockroaches tend to run along walls, but they’d only be in your way or potentially contaminate your food. Gels should be applied as small (pea-sized) drops in corners and crevices14. Bait stations should be placed against walls, in corners within cabinets and closets, on shelves, and behind and beneath furniture and appliances, including trash cans. Don’t mix different treatment types or store them together1,3,14.
Also be sure to check the label of any insecticide you’re considering to be sure it’s formulated for cockroaches. Ingredients to look for include abamectin, acephate, chlorpyrifos, cyfluthrin, cypermethrin, deltamethrin, dinotefuron, disunion, fipronil, hydramethylnon, imidacloprid, indoxycarb, and permethrin3,14,20,21.
The Hard Truth About Roach Eggs
That’s how to kill cockroach adults. How to kill cockroach eggs? The bad news: you can’t! Because insecticides won’t work on roach eggs. The oothecae protect the eggs inside, and no matter how much you try to poison them, cockroach oothecae will win out every time.
This means that if you really want to neutralize the threat that roach eggs pose, the question shouldn’t be about “how to kill roach eggs.” But about how to control the baby cockroaches (the nymphs) that are inevitably going to be born.
Focusing On Cockroach Nymphs
To control the nymphs, you’ll have to use a product that prevents them from growing or kills them as soon as they hatch. Using an insect growth regulator is one approach. When a cockroach nymph ingests a growth regulator, it won’t grow enough to reproduce. Boric acid, on the other hand, will kill newly hatched nymphs if it’s already on the egg case. In some cockroach species, nymphs will eat some of the ootheca after they hatch. Even if they don’t eat it, they will get the boric acid on their bodies and will be killed eventually anyway19.
Using The Vacuum Cleaner And The Fridge
Using insecticides in combination with the vacuum can be a very effective approach. You can vacuum up adults nymphs, and eggs3. This is most effective for small infestations and as preparation for chemical control.
Don’t just vacuum and call it a day, though. The trip through the hose won’t kill the roaches and they can just climb back out. Either put the bag in the freezer for a while or empty it into a sealable plastic container for disposal22. If you apply dusts, it’s best to avoid vacuuming for a while in case you vacuum up the insecticide.
Prolonged exposure to cold kills cockroach eggs, nymphs, and adults. If you manually collect any cockroach egg cases, you can freeze them to kill the developing nymphs22. If you know there are cockroaches in a small appliance (e.g., a toaster), put it in a plastic bag and stick it in the freezer or outdoors (if it’s wintertime). After 5 days, clean it and put it back in its place3.
Proper sanitation will also help with cockroach management. If they can’t access food and water, they will die faster1.
If you have a severe infestation, it’s recommended to call a pest control company1. Professionals come armed with special knowledge and equipment as well as years of experience.