Here are the 4 major Cockroaches you will find around Sydney.
German Cockroach
German roaches can number in their hundreds or even thousands if left to multiply. They are the smallest of all roaches found around Sydney and are distinguished by two dark stripes running down their back. They are usually found in kitchen areas where they will inhabit fridge motors, microwaves, under jug stands, and almost anything electrical that is left on for long periods of time such as phone chargers, etc. German cockroaches have the remarkable ability to maintain the development of their egg cases long after the actual roach has died. This can make total eradication difficult.
American Cockroaches
American roaches are the large red-brown flying ones that are commonly found in and around dark damp areas such as bores, drains, cavity walls, and under concrete slabs. Being the largest of cockroaches found in the Sydney area, their droppings are often mistaken by homeowners for mouse droppings, especially in kitchen cupboards. These roaches can spread diseases as well as salmonella poisoning.
Native Australian Cockroach
The "Native" Australian cockroaches found around Sydney appear to be more abundant than ever. Every suburban street in Sydney has literally thousands of these roaches under tree bark, behind palm fronds, under mulch, between sheets of fencing, and under almost any external object.
These are mostly the dark brown-black Wood roaches with one species, in particular, having a pale frill around its head. These roaches are prolific during the hot summer months when their usual supply of moisture tends to dry out making them agitated. It is during this time most homeowners notice them entering their houses for cooler air and moisture.