If you decapitate a human being, they will die almost immediately. But a cockroach? A cockroach can survive for weeks without its head.
And perhaps even more amazing is that even the head will survive, if only for a few hours, without its body.
And yes, this phenomenon has been documented by scientists who are using the decapitation experiments to study the metamorphosis and reproduction of the insects without the glandular hormones that exist in their heads. Scientists also study the bodiless heads to watch how the neurons work — they learned that the brains don’t function properly without all of the sensory input from the rest of the body.
Just how is it that the cockroach body can live without its head? They don’t have a pressurized blood system like humans. Cockroaches have an open circulatory system, so when the heads are severed, their necks are sealed off by the clotting of blood.
Nor do they breathe the same way humans do, and instead use tiny holes in their bodies called spiracles to deliver air to their tissue. Also, cockroaches are cold-blooded (poikilotherms) which means they need very little food to survive, so their last meal can keep them alive for weeks.
Not only do the headless vermin survive, but they can also stand, move, and react to tactile stimuli because of the nerve tissue or ganglia throughout each segment of their bodies. Cockroaches may not be endearing, but they are enduring, and are also infamous for their ability to withstand nuclear radiation. Apparently their cell division is much slower than that of other creatures (such as humans) and dividing cells are much more susceptible to the effects of radiation.