Cockroaches, which hide in small cracks or crevices during the daytime, can reach lengths of 18 to 60 mm depending on species. They feed omnivorously on various organic substances, including tissue, leather and paper.
The German cockroach (Blatellagermanica) is very common, and usually encountered in houses. It is relatively small and has a short life cycle of 3 to 8 months, depending on temperature. The German cockroach females carry their packages of 20 to 40 eggs with them for about 4 to 5 weeks, and then lay the eggs randomly shortly before hatching. The larvae shed their skins several times, and gradually resemble adult cockroaches more and more closely, only they are smaller and have no wings.
Cockroaches can be carriers of a high number of bacterial and viral diseases such as diarrhoea, leprosy, catarrhal colitis, infectious hepatitis, anthrax, salmonellosis, tuberculosis and fungus diseases (aspergillusflarus).
The cockroach's excrement, skin and vomit are responsible for allergies. House dust mites and cockroaches are the commonest cause of insect allergies. In the USA 10 % to 12% of the population reacts allergically to cockroaches.
Cockroaches like e.g. the Oriental Cockroach (Blattaorientalis) and American Cockroach (Periplanetaamericana) occur throughout the world, especially in tropical regions where the environment is humid and warm.