The German Cockroaches are the most common cockroaches in London as they prefer warm and humid conditions such as commercial kitchens. The Oriental Cockroach is also known as the Common Cockroach and they are probably still the most widespread cockroaches throughout the UK.
German Cockroaches are light brown with two dark stripes on the thorax, 12-15mm in length and very good climbers. The Oriental Cockroaches are a dark brown to black colour, 17-30mm in size and can survive in cooler damp areas such as basements and conduits. These common cockroaches can not climb smooth surfaces and are therefore more commonly found at ground level.
Oriental Cockroaches have a purse-shaped egg case called an ootheca that holds around 16 eggs and hatches after about 2 months. The German Cockroach egg case holds around 36 and hatches within 1 month. The ootheca of the Oriental Cockroach is dropped early in development and is often well hidden and tolerant to insecticide.
This, along with the length of time it takes to hatch and the longer life span of the adult, makes control more difficult. The German cockroach carries the ootheca almost until it hatches and this protection combined with the fact that there are over twice as many eggs and that it hatches twice as fast means that this cockroach breeds much faster although control can be easier.