Cockroaches: identifying them and getting rid of them
By day they vanish into cracks; at night, the kitchen is theirs.
The short answer
The German cockroach (Blattella germanica), the most common species in homes and commercial kitchens, is 10–15 mm long with two dark stripes behind the head. It hides close to warmth and moisture and carries germs on its legs. Treatment relies on gel bait applied in its hiding places, a second visit and the removal of cracks and water sources.
Identity card
Scientific name: Blattella germanica
- Size
- 10–15 mm (German); about 2.5 cm (oriental); up to 4 cm (American)
- Appearance
- German: light brown, two parallel black stripes on the pronotum; oriental: very dark brown to black
- Life expectancy
- Several months for the adult; several generations a year in heated premises
- Active period
- Active at night, year-round wherever there is heating
- Where it hides
- Cupboard hinges, behind appliances, sink seals, ducts, service risers
How to spot cockroaches
Tick off in your head what you have seen: the more the clues overlap, the surer the diagnosis.
- Tiny black droppings, like ground pepper, in cupboard corners and hinges.
- Empty brown egg cases, pale moulted skins and dead insects under furniture or behind the fridge.
- Brownish smears and a rancid, slightly sweet smell in heavily used hiding places.
- Insects darting into cracks the moment you switch on the light at night.
Understanding how it behaves
Three species are found most often. The German cockroach, small and light brown, lives in kitchens and bathrooms. The oriental cockroach, almost black and larger, prefers cellars, crawl spaces and bin stores. The American cockroach, reddish-brown and up to 4 cm, frequents drains and heated basements.
The female German cockroach carries her egg case (the ootheca, holding thirty to forty eggs) until it hatches. The eggs therefore escape contact insecticides, and aerosols often just scatter the insects into other rooms or next door.
Cockroaches rarely show themselves in daytime: meeting one in broad light is often a sign that the population is already large. For a restaurant or grocery, pest control is part of the hygiene obligations and must be documented.
Why it shouldn't be left
- Germs, including salmonella, carried from bins and drains onto food and surfaces.
- Allergens in droppings and cast skins, recognised as a trigger for asthma, especially in children.
- Spread from one flat to another through ducts, risers and service voids.
- For a restaurant or food business: non-compliance, or even an administrative closure if an infestation is found during an inspection.
What the technician does: cockroaches
01
Inspect
Torch inspection of hinges, seals, appliance motors and duct openings; monitoring traps to identify the species and gauge the size of the infestation.
02
Treat
Approved gel bait placed in small dots in cracks and harbourages, out of reach, with an insect growth regulator if needed; no blanket spraying in living areas.
03
Sanitise
Silicone on cracks, pipe and duct openings sealed, advice on removing standing water and leftovers that are accessible at night.
04
Follow up
A second visit is planned to reach the young that hatch from egg cases, new monitoring traps, photo report and active vigilance between visits.
Prevention, at home and at work
Simple habits that lower the risk of the intruder settling in or coming back.
- 01At home: don't leave dirty dishes, crumbs or a full pet bowl out overnight.
- 02Fix leaks and wipe the sink dry in the evening: cockroaches need water as much as food.
- 03Unpack and remove cardboard boxes quickly; check second-hand furniture and appliances before installing them.
- 04Fill cracks around pipes, behind skirting boards and splashbacks.
- 05In a restaurant: clean under and behind equipment, degrease extractor hoods and keep your pest-control plan up to date.
Your questions
How long does it take for cockroaches to disappear?
With gel bait, activity usually drops clearly within two to three weeks. The second visit targets the young born after the first application, since eggs sheltered in the ootheca are not affected at first.
Are shop-bought aerosols enough?
Rarely. They kill exposed cockroaches but reach neither the eggs nor the hidden insects, and can scatter the population. Sprayed near a gel, they also make it less attractive.
Do I need to leave during the treatment?
Not for a gel treatment: it is applied in drops inside cracks, out of reach of children and pets. The technician simply tells you which areas not to scrub for a few weeks.
Does having cockroaches mean poor hygiene?
Not necessarily. They arrive in cardboard boxes, shopping bags, second-hand appliances or through a building's ducts. A well-kept kitchen slows them down but is not enough to eliminate an established population.
Cockroaches at home or on your premises?
2-hour slot, 7 days a week from 8 am to 8 pm, price shown and paid online, photo report emailed on the day of the visit.
Related service: Crawling insect treatment
