The short answer
The German cockroach is common in Hong Kong kitchens. Key identifiers are a pale-brown body, an adult length of 1.3–1.6cm and two dark parallel stripes just behind the head. It rarely flies. It hides in warm, damp gaps — behind the fridge motor, inside oven seams, behind the water heater — and can breed quickly. Record repeated sightings and inspect nearby hiding places. Gel bait and targeted treatment may suit hidden activity better than spraying only the insects you can see.
- Scientific name
- Blattella germanica
- Chinese name
- 德國曱甴
- English name
- German cockroach
How to identify a German cockroach
- Size: adults run 1.3 to 1.6cm, nymphs smaller, pale brown to tan.
- The giveaway mark: two dark parallel stripes on the shield just behind the head — the main way to tell it apart from an American cockroach.
- Wings: present but rarely used for flight — it mostly crawls.
- Spotting one is rarely a one-off — German cockroaches breed fast, and a single egg case can hatch dozens of nymphs.
Where do they turn up in Hong Kong homes and shops?
German cockroaches almost never survive outdoors — they stay in warm, damp indoor gaps, especially kitchens:
- Behind the fridge or washing machine motor
- Inside oven or microwave seams
- Behind the water heater or extractor fan joints
- Cabinet and counter joints
- Prep counters and cold room doors in food businesses
Why does it matter?
The main issue with German cockroaches is food contamination and allergens — the residue and droppings they leave behind are a common indoor allergen — sensitive people may experience asthma or eczema-type reactions (that doesn't mean everyone in an affected home will react). For food businesses, being spotted by a customer is its own reputational risk.
Does spraying insecticide yourself work?
Surface spray usually kills only what it touches — anything hiding in a gap, plus the egg cases, goes untouched and hatches again weeks later. The professional approach generally uses gel bait plus residual treatment worked into the gaps, so the roaches carry the bait back to the nest themselves and the source gets treated. For a fuller comparison, see our cockroach DIY vs professional guide.
How to keep them from coming back
- Keep food sealed and don't leave it out overnight
- Wash dishes right after use — don't leave them overnight
- Clean crumbs from behind the fridge and under the oven regularly
- Don't stockpile cardboard boxes or paper bags in the kitchen — roaches like the corrugated layer inside