There are four cockroach species most commonly found in Chinese households.
The first, and most common, is the German cockroach (*Blattella germanica*), only 1–1.
5 cm in length, light brown, with two longitudinal dark stripes on the pronotum.
It is the most widely distributed and most difficult cockroach to control globally, reproducing extremely rapidly—a single female can carry 4–8 oothecae (egg cases) in her lifetime, each containing 30–40 eggs.
The German cockroach relies almost entirely on human dwellings for survival.
The second is the American cockroach (*Periplaneta americana*), 3–5 cm long, reddish-brown, the largest of the common indoor cockroaches.
It prefers more humid environments and is often found in sewers, basements, and ground-floor bathrooms.
The third is the smoky-brown cockroach (*Periplaneta fuliginosa*), medium-sized, dark brown to black, and tends to be more of an outdoor invader, particularly common in southern regions.
The fourth is the Australian cockroach (*Periplaneta australasiae*), similar to the American cockroach but slightly smaller, with a distinct yellow stripe along the leading edge of the forewing.
It also prefers warm, humid environments and is more common in southern cities.
Different cockroach species have different behavioral preferences, so identifying the species helps in targeting control efforts.