While most of the 200-plus species are bush cockroaches, the best-known members of this family are the introduced pests. The large (40 mm), shiny red American cockroach, Periplaneta Americana and the so-called Australian cockroach, P. australasiae, which originated in Asia, are an integral part of domestic life. P. australasiae can be recognized by a yellow band across the base of the pronotum and yellow slashes along the base of the forewings. Their effective diurnal hiding and the ability to fly into new territory make them all but impossible to eradicate. Among the bush cockroaches are many large, wingless genera. These fat, sometimes colourful, cockroaches are often diurnal and clamber about on the bushes they feed on. Many can emit a powerful defensive chemical smell. Polyzosteria and Cosmozosteria have some very striking, flightless, sometimes metallic-coloured species.
Incomplete life cycle; small to large (3-70 mm in length); broad, flattened body with the pronotum forming a shield usually overhanging the body on the sides and partly the head; wings, when present, are membranous with toughened forewings which overlap left over right; head has mandibulate mouthparts, pointing downwards and with the ocelli reduced to two lensless points between the eyes; legs are long, spined and adapted for running.
The general form of cockroaches varies little. Therefore, the image of the introduced city dwelling species helps to place the majority of the native bush species in this order.
Source: A field guide to insects in Australia - third edition - Paul Zborowski and Ross Storey - New Holand publishers