The 2 most likely cockroaches to be encountered in the UK are the German and the Oriental Cockroaches. Although a few other species could be encountered treatment would be the same.

Cockroaches have been great pests in domestic dwellings for centuries and are always difficult to eradicate, largely because of their secretive and nocturnal habits. They will only be seen occasionally during the daytime, and the destruction of these does little to reduce the population. They live during the day in cracks and crevices, behind tiles, in refrigerator motors, junction boxes, light fittings etc. If cockroaches are seen regularly during the day then the infestation is usually quite serious as they are nocturnal. The 2 most likely cockroaches to be encountered in the UK are the German and the Oriental cockroaches. Although a few other species could be encountered, treatment remains the same. Cockroaches are common in commercial premises associated with the production or handling of food. Gregarious and nocturnal, they spend the day hiding in cracks and crevices around such areas as sinks, drains, cookers, the backs of cupboards and in refrigerator motor compartments. They especially favour buildings with service ducts and complex plumbing installations. Infestations may be introduced through incoming laundry, on raw materials, in crates and packaging, or arise as the insects enter the buildings via such routes as drains or refuse chutes.

The adult is 10-15 mm long, yellowish-brown with wings well developed on both sexes. The wings are never used. It is an excellent climber on both smooth and rough surfaces. The female of the species produces 4-8 egg capsules at monthly intervals. Each capsule contains about 30 eggs, which the female carries with her until just before hatching, which then takes 2-4 weeks. Efforts are made to conceal the capsule near a food source, where the nymphs will hatch and pass through 5-7 moults before reaching maturity. At a temperature of 25C maturity is reached in 3.5 months, but this time is subject to great variation depending on the temperature. Adults live approximately 8.5 months at 25C.

The German cockroach is particularly successful for the following reasons: the large number of eggs per capsule. The female protects the egg capsule, by carrying it until just before hatching. Short development period to hatching and maturity. Small size, therefore readily conceals itself. The German Cockroach prefers warm moist conditions (25-31C) such as occur in kitchens and restaurants. For this reason it is sometimes known as the steam fly. It moves quickly and climbs with ease, thus it will be found in harbour ages on vertical and upside-down surfaces, in cracks and crevices, behind panels and notice boards, in drawers and cupboards, inside electrical equipment and machinery.

Adult, 20-24 mm long, dark brown, nearly black. Wings of male cover two-thirds of abdomen. Wings of female are vestigial and she cannot fly. Both can climb rough but not smooth surfaces. The female produces 5 egg capsules at monthly intervals. The thick walled resistant capsules, 12mm in length, each contain up to 16 eggs and are cemented to the substrate in the vicinity of a food supply, and may be covered over with debris. Nymphs emerge 6-12 weeks later and progress through 7-10 moults before reaching maturity, a process which takes 10 months to 2 years depending upon temperature and food supply. Adults live approximately 4.5 months at 25C. The slow proliferation of the Oriental cockroach will limit its success where reasonable standards of hygiene exist. The Oriental cockroach will tolerate lower temperatures than the German, but will tolerate higher temperatures as long as water is available. It is largely being replaced by the German, which is a better climber and faster breeder.