Cockroaches Can Live Without Their Heads

The immediate and catastrophic effect of decapitation in humans is due to a massive drop in blood pressure and the loss of the brain, which controls critical functions like breathing. For a cockroach, however, the story is entirely different. They have an open circulatory system with much lower blood pressure, so the wound at the neck simply clots without the dramatic blood loss seen in mammals. Furthermore, their nervous system is decentralized, with clusters of nerve tissue called ganglia distributed throughout the body that control basic reflexes. This means the body can continue to react to stimuli even after its connection to the main brain is severed.

This unique biology extends to how they breathe. Instead of a single mouth and lungs, cockroaches take in oxygen through a series of small holes called spiracles located on each body segment. These spiracles connect to a network (Review) of tubes that deliver oxygen directly to the insect's tissues. Because this respiratory process is completely independent of the head, the headless body can continue to "breathe" for an extended period. The ultimate cause of death for the decapitated cockroach isn't asphyxiation or blood loss, but simple dehydration. Without a mouth to drink water, it will perish from thirst, a process that can take up to a week.