The cockroaches are an ancient group, dating back at least as far as the Carboniferous period, some 320 million years ago. There are about 30 cockroach species out of 4,600 are associated with human habitats. In Australia, three species are most common and well known as household pests: German cockroaches, American cockroaches and Australian cockroaches.
The German cockroach is a small species of cockroach, the German cockroach adults can grow up to 1.6 cm long. In colour it varies from lightly brown to almost black. Although it has wings, it can not fly. The German cockroach has very short breeding cycle, it reproduces faster than any other residential cockroach. Each egg case may contains up to 40 eggs. Under favourable conditions, It only takes as short as 40 days to grow from egg to reproductive adult. This is why the population of German cockroach increase incredibly fast in infested areas. German cockroaches are attracted particularly to meats, starches, sugars, and fatty foods. Where a shortage of foodstuffs exists, they may eat household items such as soap, glue, and toothpaste. In famine conditions, they turn cannibalistic, chewing at each other’s wings and legs. In a domestic property with German cockroaches infestation, they can be easily found in kitchens where closed to the food source, they can also be found in bathroom and laundry room where they can find water to drink. In a heavy infestation situation, they can even be found in bed rooms as they try to forage for food and look for shelters. German cockroaches are the most common and troublesome pest in commercial restaurants.
The American cockroach is the largest species of common cockroach. American cockroaches can grow up to 53mm long. They are reddish brown and have a yellowish margin on the body region behind the head. American cockroach nymph emerge from egg cases in 6–8 weeks and require 6–12 months to mature. American cockroaches eat a great variety of materials such as cheese, beer, tea, leather, bakery products, starch in book bindings, manuscripts, glue, hair, flakes of dried skin, dead animals, plant materials, soiled clothing, and glossy paper with starch sizing. They prefer fermenting foods. They have also been observed to feed upon dead or wounded cockroaches of their own or other species. The American cockroach can fly and it is one of the most fastest running insects. They normally live in moist areas, but can survive in dry areas if they have access to water. These cockroaches are common in basements, crawl spaces, cracks and crevices of porches, foundations, and walkways adjacent to buildings. In residential areas outside the tropics these cockroaches live in basements and sewers, and may move outdoors into yards during warm weather.
The Australian cockroach is brown overall, with the tegmina having a conspicuous lateral pale stripe or margin, and the pronotum with a sharply contrasting pale or yellow margin. It looks similar to the American cockroach but slightly smaller. It has a yellow margin on the thorax and yellow streaks at its sides near the wing base. It often lives around the perimeter of buildings. It appears to prefer eating plants more than its relatives do, but can feed on a wide array of organic (including decaying) matter.