Ans.

Even for major catastrophes like losing a head, cockroaches don’t bleed very much. Unlike humans, they have an open circulatory system: A system for distributing blood through their bodies that doesn’t depend on a closed network of arteries and veins. Their blood doesn’t pump under pressure like ours, but just sort of sloshes around, making its way into the cockroach’s tissues. The great thing about this system, if you’re someday going to be headless is that when a major wound occurs, blood doesn’t suddenly get forced out. For a cockroach that loses its head, the blood just clots at the neck. The cockroach will have a nasty scab for sure (where its head used to be), but it won’t die from loss of blood. Unlike humans, cockroaches don’t breath through a nose or their mouth. Instead they breathe through small holes in their bodies called spiracles that don’t need a brain to direct them. No nose, no mouth, and no need for a brain to regulate your breathing means that you can breathe all you want to without a head. But it is going to die from being unable to eat. And well before that, it’s going to die from thirst. A headless cockroach has no mouth to drink with and will be dead from dehydration in less than a week. Which brings the total day count from the moment it loses its head to the moment it loses its life to somewhere around 7 days or less.