Cockroaches are insects of the order Blattodea, There are 3 common cockroaches in Singapore, German Cockroaches, American Cockroaches and Oriental Cockroaches.
Blattella germanica inhabits normally in buildings, but is particularly associated with restaurants, food processing facilities, hotels, and institutional establishments such as nursing homes. These cockroaches are unable to withstand the cold climates.
Though nocturnal, the German cockroach occasionally appears by day, especially if the population is crowded or has been disturbed. However, sightings are most frequent of an evening, when someone suddenly brings a light into a room deserted after dark, such as a kitchen where they have been scavenging. When excited or frightened, the species emits an unpleasant odor.
The oriental cockroach (Blatta orientalis), also known as the waterbug, is a large species of cockroach, adult males being 18–29 mm (0.71–1.14 in) and adult females being 20–27 mm (0.79–1.06 in). It is dark brown to black in colour and has a glossy (shiny) body.
The female Oriental cockroach has a somewhat different appearance from the male, appearing to be wingless at casual glance but has two very short and useless wings just below her head. She has a wider body than the male. The male has long wings, which cover two thirds of the abdomen and are brown in color, and has a narrower body. The odd male is capable of very short flights, ranging about 2 to 3 meters.
American cockroach adults grow to an average length of around 4 cm (1.6 in) and about 7 mm (0.28 in) tall.They are reddish brown and have a yellowish margin on the body region behind the head. Immature cockroaches resemble adults except they are wingless.
The cockroach is divided in three sections; the body is flattened and broadly oval, with a shield-like pronotum covering its head. A pronotum is a plate-like structure that covers all or part of the dorsal surface of the thorax of certain insects. They also have chewing mouth parts, long, segmented antennae, and leathery fore wings with delicate hind wings. The third section of the cockroach is the abdomen.
The insect can travel quickly, often darting out of sight when someone enters a room, and can fit into small cracks and under doors despite its fairly large size. It is considered one of the fastest running insects. It has a pair of large compound eyes, each having over 2000 individual lenses, and is a very active night insect that shuns light.