Walking through, and eating all kinds of filth, these insects will happily transmit diseases on their feet or in their faeces.
Due to their small size cockroaches are able to hide in cracks, ducting, behind or underneath refridgerators or under floors or in ceilings. German Cockroaches carry their eggs with them almost up until the point at which they hatch whereas Oriental Cockroaches deposit their egg cases as they move.
The act of scattering their egg cases makes them harder to eliminate. When German Cockroaches die their eggs will mostly die with them.
The Oriental Cockroach egg case, deposited away from the adult, has resilience. Once all the adults are long dead, the eggs hatch and the young appear ready to reinfest the property once more.
Cockroaches will eat anything they can get into their mouthparts. Even the cleanest of domestic kitchens can be susceptible to infestation with food particles falling down the back of cupboards or under kitchen countertops.
Cockroaches need to be 100% removed or reinfestation can occur making it difficult to get rid of these pests.