German cockroaches: a plain-language guide
What German cockroaches look like, how they breed, where they hide, and what actually works.
German cockroaches are the roaches most people in Ontario have to deal with indoors. They are small, quick and good at staying hidden. This guide explains how they live, so you can see why a one-time spray rarely works.
Quick profile
- Size: about 1.3 to 1.6 cm long
- Colour: tan to light brown
- Key mark: two dark stripes behind the head
- Wings: yes, but they do not fly
- Where: indoors, near food, water and warmth
- How they spread: with people, through bags, boxes, groceries and used furniture
If you want the overview first, start with cockroaches.
What is their life cycle?
Egg case
A German cockroach female carries her egg case at the rear of her body until just before the eggs hatch. Rutgers extension reports about 40 eggs per case. Because she carries it, it is protected while she hides.
Nymphs
The young are called nymphs. They are wingless and darker than adults, with two dark stripes around a lighter patch behind the head. They shelter in cracks and grow by shedding their skins.
Adults
Adults are tan with wings. From egg to adult takes about 100 days, according to the University of Florida, and there can be three to six generations in a year. That is why a small problem becomes a big one so quickly.
How fast do German cockroaches breed?
Quickly. With about 40 eggs per case and several generations a year, numbers can grow fast, especially in warm kitchens with a steady food supply. This is also why early action matters.
Why do they thrive in apartments?
They do not move in from outdoors. People carry them, and in apartment buildings they also travel through shared walls, pipes and wiring. Kitchens and bathrooms in neighbouring units are connected. One untreated unit can keep restocking the others.
Where do they hide?
Kitchen
University of Florida lists common hiding spots behind refrigerators, freezers, ovens and stoves, inside wall voids, under loose sink plates, and in hollow furniture legs and cardboard. Health Canada adds cracks, crevices and pipe openings near food.
Bathroom
Dark, damp spots work for them: under the vanity, around the toilet base and around pipes. Fix leaks and run the fan to cut moisture.
How do they get in?
Mostly by hitchhiking. Health Canada notes they arrive on used furniture, food items, empty bottles and shipping cartons, sometimes as egg cases. They are also active at night, so a group can grow unseen for a while.
What helps: sanitation, moisture and sealing
Cleaning will not remove an infestation, but it makes treatment work better. Health Canada’s steps include:
- Clean up spills right away.
- Store food in sealed plastic or glass containers.
- Seal garbage and empty it daily.
- Do not leave dirty dishes overnight.
- Vacuum often, fix leaks and ventilate bathrooms.
- Seal cracks and gaps to remove hiding places.
Why are they so hard to kill?
They hide in tiny spaces, breed fast and the egg cases protect the next generation. Roaches can also become resistant to a product that is used over and over. Rutgers advises alternating products with different chemical classes to slow that down.
How do professionals treat them?
Extension guidance for German cockroaches is built around monitoring, sanitation and baits, with follow-up visits. Our approach is IPM:
- Inspect and monitor, often with sticky traps in likely spots.
- Identify the species.
- Treat with baits, growth regulators and sealing, rotating products when needed.
- Follow up every two to four weeks as needed, until no roaches have been seen for about a month.
See our cockroach control page for what to expect.
Landlord and tenant rules
In Ontario, landlords must deal with pests such as cockroaches as part of keeping a unit in good repair. In Toronto, apartment building owners must inspect common areas for pests at least every 30 days. They must also inspect within 72 hours of learning a pest has been reported, and hire a licensed company where required. Tell your landlord in writing and keep a copy.
Restaurants and food businesses
Food premises need a plan that fits their kitchens and inspections. See commercial pest control.
Next step
Seeing German cockroaches? Send the free quote form or call us. You get price details or a call-back in under 30 minutes.
Common questions
Do German cockroaches fly?
They have wings, but they do not fly. They run fast and hide quickly instead. If you see a roach flying, it is probably a different, larger species. Tell your technician what you saw so the species can be confirmed.
How can I tell a nymph from a baby beetle?
Nymphs are wingless, darker than adults, with two dark stripes around a lighter tan spot behind the head. They run quickly and stay close to cracks. Beetles are usually rounder with hard shells. A sticky trap can catch a sample.
Does bleach kill them?
Not reliably. Bleach may kill a roach it touches, but it does not reach those hiding in walls, or the egg cases. It can also be unsafe near food or when mixed with other cleaners. Use sanitation plus professional baits instead.
Can they live in electronics?
Yes, they like warm, tight spaces near food and water, and extension sources list electrical junction boxes and appliances as hiding spots. Do not open or spray electronics. Let your technician advise.
How long to see results?
You may notice fewer roaches within days, but clearing an infestation takes weeks. Extension guidance is to follow up every two to four weeks until none are seen for about a month. Results depend on how large the problem is.
How do I stop them returning?
Keep food sealed, fix leaks, seal cracks and pipe openings, and check boxes and used items before you bring them in. Because people spread them, shared buildings need everyone on board. Ask about follow-up checks after treatment.
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