Roaches are notoriously difficult to get rid of, much less kill. They can bounce back from insecticides, recover from being stepped on, and even regrow limbs. Although roaches can’t survive a direct nuclear blast, they can withstand radiation for longer than humans. Because of all this, you might think the only way to kill a roach is to chop off its head.
A cockroach will live for a few days or up to 3 weeks without its head. Its anatomical makeup allows it to breathe, endure starvation, and resist dehydration for long periods without its head. In this state, cockroaches can’t eat, but they’ll use energy and fat storage from within their body to live. They survive dehydration by slowing their respiration to prevent water loss. Since roaches take in oxygen through abdominal spiracles, they don’t even require a head to breathe.
To make things worse, headless cockroaches will not even bleed to death. Their vascular systems are built to avoid critical drops in blood pressure and uncontrollable blood loss. That is usually what makes decapitation lethal. Even still, a headless roach will eventually die from starvation or dehydration, whichever comes first.
- 1 How Does a Cockroach with No Head Breathe?
- 2 How Long Can a Cockroach Live Without Its Head Before It Starves to Death?
- 3 Will a Headless Cockroach Bleed to Death?
- 4 Can Headless Cockroaches Live For Weeks?
How Does a Cockroach with No Head Breathe?
Roaches can survive without a head partly because they do not require their head to breathe. Instead, they take in oxygen through pockets spread across their abdomen. These stretch into their bodies as ‘tubes,’ which are called spiracles.
A cockroach’s respiratory system is very different from that of mammals. The spiracles are the primary valve in which oxygen and carbon dioxide are exchanged. These spiracles are located on the cockroach’s body, instead of being linked directly with the head. Oxygen enters the body through these passages, with carbon dioxide being expelled out.
If the roach loses its head, this process continues anyhow. The body is given all the oxygen it needs. It doesn’t rely on any mouth or nose to do that job.
Aside from that, there are 2 other physiological differences. These allow roaches to breathe with no head:
They Do Not Require Nerve Cells To Breathe
As humans, we rely on our nerve cells to control muscular functions, breathing included. Cockroaches do not use nerve cells to direct their body to breathe. As such, they can breathe without signals from their brain. This is known as “passive breathing.”
Their Blood Does Not Carry Oxygen
Cockroach blood does not carry oxygen throughout the body. These insects count on their functioning spiracles to intake air. As such, if their body needs to close down its blood flow and isolate it to certain areas of the body, it doesn’t suffer from oxygen deprivation.
How Long Can a Cockroach Live Without Its Head Before It Starves to Death?
Roaches can survive for up to 3 weeks without a head. It won’t be able to eat or find food, so it will starve. Likewise, it won’t be able to find and drink water, so it will die of dehydration. That is what actually kills the roach, not the decapitation.
With that in mind, there are cases where headless roaches die in a matter of days. This depends on:
- How well-fed the roach is
- How much water the roach consumed before it was decapitated
Since roaches are unable to properly detect or avoid predators while headless, this can also lead to a swift death. Once the body is ‘killed,’ that is when the roach is considered dead. The head itself will be unable to move, so it can suffer the same fate.
Many sources argue that headless cockroaches can live for months. In a scientific context, the answer is less clear-cut. According to the Entomology Department at the University of Illinois, there have been numerous studies conducted on decapitated cockroaches. They focused on:
- Hormone and sex pheromone synthesis
- Gamete (or sex cell) growth
- An array of behavioral phenomena
Despite this, no current studies have a direct answer to how long a decapitated roach survives. Instead, we can estimate how fast its death-clock ticks based on how it can endure starvation and dehydration. In fact, you could even say that roaches would survive forever without a head, if it weren’t for those two problems:
Cockroaches rely heavily on water to survive. Dehydration will usually be the first thing to kill a roach when its head is chopped off. However, it can still take days or weeks to finish the bug. That’s because water loss in cockroaches happens in three different ways:
- Respiratory gas exchange
- Maintenance of their protective outer coat
Headless cockroaches should lose water mostly by breathing through their spiracles. After all, there is less food to excrete or act as a supply for their outer shell. According to the Journal of Experimental Biology, cockroaches slow their breathing rate to preserve water. This prolongs their survival when they’re headless or cut off from water sources alike.
This study did not decapitate their cockroach subjects. However, we do know that cockroaches rely only on their spiracles to breathe. By understanding how long they take to die of thirst, we can accurately guess how long they can live without a head.
The more hydrated they are before they’re decapitated, the longer they will last. This was discovered by another study published under the Journal of Experimental Biology. As such, limiting the amount of access a roach has to water before decapitating it will kill it faster. It won’t have the same reserves to fall back on. Dehydration will kill off the roach long before the physical damage does.
Roaches are able to survive for over a month without food. This timeline can become even longer if the roaches find untraditional food sources. As an example, paint chippings or even dead skin cells will serve as temporary nutrients to keep a roach trucking along.
With that said, headless roaches are unable to eat. Without the use of antennae and eyes to guide it, the body will wander aimlessly. It will be able to detect vibrations and a few scents, but it will be mostly trial and error. Even if it locates food, it will be unable to eat it without a head and, therefore, mandibles.
Because of that, if subjected to starvation alone, most headless cockroaches would survive for about 3 weeks. Arthropod Structure & Development discovered some of the physiological mechanisms behind this. For example, when roaches are barred from food:
- Glycogen and lipid stores are mobilized until death
- Trophocytes and fat lobes shrink over time
- Endosymbiotic bacteria aid amino acid synthesize, creating another source of potential energy
Glycogen serves as the primary storage of energy in many invertebrates. Lipids, or fat, are also good sources of energy. In cockroaches, both glycogen and lipids are stored in “fat bodies.” Larger fat bodies concentrated near their intestines, gut tubes, and reproductive organs.
Trophocytes are the cells that make up cockroach fat bodies. Those, as well as fat lobes, are observed to shrink during food deprivation. This helps cockroaches to save as much fat as they can while they’re starving.
Additionally, endosymbionts are bacteria that coexist peacefully within the cockroach. These are known to synthesize amino acids. Amino acids act as additional energy sources to roaches, particularly when glycogen and lipid storages are low. This further allows the cockroach to endure long bouts of starvation.
Starved cockroaches were able to mobilize the nutrients in their fat bodies for about 2 weeks. Most died at the 3-week mark. There were no surviving cockroaches past 7 weeks.
Do Headless Female Roaches Survive Longer Than Males?
Interestingly enough, the Journal of Invertebrate Physiology found that starved female cockroaches lived longer than starved males. This is possibly due to the larger amount of fat stores that they have in comparison.
Cockroaches with more fat storage have more energy to use during periods without food. As such, they live longer. Biologically, this makes sense, as female cockroaches are responsible for producing eggs. They require more nutrients to do so, and can repurpose those at will.
Roaches can also survive for long periods while headless and starving because they are poikilotherms. This means that they cannot regulate their internal body temperatures. They are heavily reliant on the temperatures of their environment. Poikilotherms are also commonly described as cold-blooded. The main difference between warm-blooded and cold-blooded organisms is their metabolic requirements.
Maintaining a warmer blood temperature requires energy. Energy is acquired through the food a creature eats and then converts into usable chemicals during metabolism. However, much of the heat energy attained from food is lost to the environment. That’s why warm-blooded animals, such as humans, need to eat a decent amount of food per day.
Cold-blooded organisms, like roaches, do not need to regulate their internal temperature. As such, they do not require nearly as much food as a warm-blooded organism does. This allows for the cockroach to survive for long periods of time without eating. Therefore, being headless will not impact their survival capabilities significantly. They are built in such a way that allows them to be less dependent on food.
Will a Headless Cockroach Bleed to Death?
Forget starvation; won’t a cockroach bleed to death before they starve to death? The answer is no. That’s because a cockroach’s vascular system is responsible for carrying blood throughout the body. It is far different from mammals and helps prevent headless cockroaches from bleeding to death.
In humans, our blood vessels are extensive, intricate, and extremely tiny. Because of this, we require high blood pressure to pump blood through all of our tiny vessels. If a human were to be decapitated, we would die from intense blood loss and a severe drop in blood pressure. Likewise, our brain would be disconnected, and our ability to breathe would immediately cease.
The same isn’t true for roaches. Although they’re tiny creatures, their blood vessels are not small. Thus, they do not need high blood pressure to circulate their blood. Lower blood pressure ensures that blood loss is not uncontrollable when decapitated.
Additionally, they do not have a complex vascular system. A smaller number of blood vessels mean a smaller number of “exits” that blood can leave through when opened. If a cockroach is decapitated, blood will leave slowly and cannot empty in a sudden gush.
Therefore, a headless cockroach will not bleed to death. Their blood pressure does not drop to critical lows, and their blood loss is not uncontrollable. In fact, their necks will just clot up and seal before they can bleed to death.
Can Headless Cockroaches Live For Weeks?
Roaches can live for several weeks without a head. If it were able to eat and drink in your home, its body would be well-stocked for this moment. It will simply absorb the fat stores in its body and avoid water loss by slowing its breathing.
The severe-point for the head and body will just clot up. The body will then proceed to wander through your home, guided by natural instincts. It will try to find food, shelter, and water like normal. It will struggle to detect predators and be unable to eat whatever food is located.
The head, meanwhile, will stay behind. If the decapitation process did not crush it, it will twitch and look around. With fewer fat stores to rely on, it will die much more quickly.
Cockroach Head Chopped Off
Chopping off a roach’s head is an effective way to kill it. There is no way for the cockroach to regrow its head or regain its ability to eat. It will just be a matter of time before it wastes away.
However, the roach can still spread disease and navigate throughout your home. If you’ve decapitated a roach by accident, be sure to finish the job. Spraying the roach with insecticide is one option, but crushing it is more effective. This will keep it from walking or fluttering away.
Once its main body is crushed, its organs will rupture, and the cockroach will die. Even if the crushing effect does not kill the roach, it will at least be immobilized. The body will become as harmless as the head while it waits for death.