There are thought to be around 4,000 known species of cockroach in existence but only about 30 of the different species of cockroach are the ones that humans come into contact with. Cockroaches are generally not keen on close contact with humans and are only really present if there is enough for them to eat.
The cockroach is dated around 300 million years old, with fossil evidence suggesting that the modern cockroach is much smaller than the original roach. Today the cockroach is on average, about an inch long.
The cockroach is an omnivorous animals and feeds on decaying matter and therefore is often associated with things being dirty (you would not be happy to find them in a restaurant for example). Most cockroach species are nocturnal with the exception of the oriental cockroach, which is attracted to light. Cockroaches generally only eat organic matter but some have been known to even eat substances such as mouldy wallpaper paste.
Due to it's small size and abundance, the cockroach is prey to numerous predators around the world including birds, spiders, small mammals and reptiles. The cockroach is even eaten by humans in some cultures and regions of the world.
Cockroaches are thought to be able to have up to four litters of young every year. The female cockroach lays between 10 and 90 eggs per time, which hatch in a matter of days. It takes just a month for the baby cockroach to become an adult cockroach. Female cockroaches are distinguishable from male cockroaches as the female cockroaches have a more rounded abdomen.
Unlike most other animals, the brain of the cockroach is in its body instead of its head. This means that a headless cockroach can live for nearly two weeks and will eventually die from malnutrition and not nerve damage.