The short answer
The American cockroach is the large roach you sometimes see in Hong Kong — reddish-brown, glossy, adults 3.5 to 4cm long, capable of short flights, and a different species from the small German cockroach. It's mostly an outdoor insect, living in drains, septic systems, refuse rooms and back lanes, and it enters flats through drains and pipework — which is why spraying indoors alone rarely gets rid of it for good; the drain is where the source needs treating.
- Scientific name
- Periplaneta americana
- Chinese name
- 美洲曱甴
- English name
- American cockroach
How to identify an American cockroach
- Size: adults run 3.5 to 4cm long — the largest cockroach commonly found indoors in Hong Kong.
- Colour: reddish-brown and glossy, with a pale yellow ring around the edge of the shield behind the head.
- Flight: adults have wings and can fly short distances, especially when startled.
- Fast-moving, and drawn to smooth walls and drain areas — a very different profile from the small, gap-dwelling German cockroach.
Where do they turn up in Hong Kong?
American cockroaches mainly live outdoors and in drainage systems, unlike the indoor-dwelling German cockroach:
- Drains, floor gullies, septic systems
- Refuse rooms, back lanes, ground-floor drainage points
- Basements and car parks
- Restaurant back doors and near grease traps
- After heavy rain or damp weather, they'll also climb pipework up into bathrooms and kitchens on higher floors
Why does it matter?
American cockroaches live in environments that carry bacteria by nature — drains and refuse — so contact with cookware or tableware raises hygiene concerns. Their large size and ability to fly also make a sighting far more visible in a home or restaurant, which is a real reputational and hygiene-score risk for shopfront businesses near back lanes.
Why doesn't spraying indoors alone work?
The nest is usually not inside your flat at all — it's in the drainage system, so indoor spraying only deals with the few that already crawled in, and the source is untouched. The effective approach is drain mesh covers, residual treatment of drainage points, and outdoor bait stations — treating the source rather than just chasing what's already indoors. See our cockroach control service for details.
How to keep them from coming back
- Fit mesh screens over floor gullies and drain covers
- Keep back lanes and shopfronts dry — avoid standing water
- Keep bins covered and don't leave them out overnight
- Buildings and neighbouring shops can share the cost of regular drain treatment — one shop acting alone rarely solves it long-term