Cockroaches are close relatives of termites and belong to the insect Order Blattodea. They represent a primitive and highly successful group of animals whose origins extend back at least 300 million years. Fossil evidence suggests that little change in their general body form has occured since that time.
As a group, cockroaches have exploited a diverse range of ecologies, living among decaying leaf matter, under bark, in caves and burrows, on the foliage of shrubs and in the nests of social insects, boring into wood and even adopting a semi-aquatic habit. A few species have invaded the dwellings of humans, in some cases to become very successful scavengers that cohabit with people in many, if not most, human communities around the world.
Despite their somewhat misleading common names, most pest cockroaches that occur in Australia and many other countries probably originated in tropical or subtropical Africa. Their wide distribution is attributed to transport in ships, carriages, and later trains and aeroplanes, facilitated by a remarkable degree of adaptation to build environments. In dwellings and various utilities for waste disposal, people have created conditions that make food, shelter and often suitable temperatures available to these very opportunistic insects. Their wide distribution and close association with humans, coupled with the high frequency with which they carry human diseases, in and on their bodies, have given them a very high pest status in most parts of the world.