Believe it or not, a cockroach can survive weeks before dying, whereas if a human were decapitated, we would die in a matter of minutes.
Why is that? Well cockroaches are very small. Plus, humans have lots of blood vessels and capillaries... which means we would be prone to bleeding to death and dying from the blood vessels not being supplied with oxygen since the main control center for giving oxygen would be that brain- which is no longer part of the body.Not to mention that since our mouth is on our head which is separated from our body, we can't eat, thus making us die from starvation. Cockroaches don't need that food so starvation would start taking effect after a week!
So that is why Cockroaches can survive for weeks without their heads! So if you catch a cockroach.... don't cut off their heads or else you will be truly doomed!