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Why does a cockroach not die after its head is cut off?

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    $\begingroup$ Could you give a citation referring to this fact? $\endgroup$
    – AliceD ♦
    Commented Nov 9, 2014 at 13:21

3 Answers 3

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Based on an article here, unlike humans, cockroaches have an open circulatory system. They don't have a huge network of blood vessels like that of humans, or tiny capillaries that you need a lot of pressure to flow blood through. Hence after you cut their heads off, very often their necks would seal off just by clotting.

According to the article cockroaches breathe through spiracles, or little holes in each body segment. Plus, the roach brain does not control this breathing and blood does not carry oxygen throughout the body. Rather, the spiracles pipe air directly to tissues through a set of tubes called tracheae. In addition cockroaches are poikilotherms, or cold-blooded, meaning they need much less food than humans do. Hence cockroaches can survive decapitation.

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Although the answers to date are all factual and sufficient to answer the question why cockroaches would live without its head, some answers don't seem to be necessary as explanations.

Summarizing the given answers so far.

  1. Roaches' simple circulation would still function without its head.
  2. Roaches' decentralized respiratory system can still function without its head.
  3. Roaches are cold-blooded and demand less energy.

However, chickens can live without its head as long as the injury does not significantly damage its brain stem, which controls the animal's vital reflexes such as respirations.

  1. Chickens do have complex network of blood vessels and capillaries.
  2. Chickens don't breathe via spiracles and do have centralized respiration system like us.
  3. Chickens are warm-blooded.

Thus, an animal (such as a cockroach) can live headless if its remaining organs can still control its "vital functions".

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  • $\begingroup$ "Thus, an animal (such as cockroaches) can live headless if the remaining organs can still control its "vital functions".- until & unless it's internal food resources are depleted... $\endgroup$
    – souvik bhattacharya
    Commented Nov 20, 2014 at 3:14
  • $\begingroup$ @souvik bhattacharya However, Mike the Headless Chicken from SYK's link finally died by suffocation. It could eat if fed. $\endgroup$
    – BartekChom
    Commented Jan 18, 2015 at 11:07
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Cockroaches are insects which means their brain is distributed.

The predominant characteristics of the cockroach central nervous system (CNS) are its segmented nature and decentralization of control processes (Ganihar et al., 1994; Pipa & Delcomyn, 1981)

. There is a pair of ganglion on each segment- head, thorax and abdomen. The ganglion on head is controlling the antennae inputs,proboscis,mandibles,eyes etc. When we cut off its head the ability to control all the above described organs fails(although, that doesn't matter because these organs are also decapitated) & it can't eat.. but the ganglion on the thorax is actually responsible for the breathing and digestion of food(with the help of ganglion on the abdomen). So if there is any food in the gut it will be normally digested and cockroach can live days consuming this energy. Also when head is gone there is no need to provide resources for the organs in head. So it can live more days by saving these resources.Plus, it can copulate if it is placed properly and this copulation is controlled by the ganglion on the abdomen.

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    $\begingroup$ Hello and welcome to SE Biology! It would be great if you added some references to support your response! $\endgroup$
    – Behzad Rowshanravan
    Commented Nov 19, 2014 at 12:32
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    $\begingroup$ It's part of writing a good answer @souvikbhattacharya, Bez is perfectly right to request this - consult the help pages $\endgroup$
    – rg255
    Commented Nov 19, 2014 at 14:35
  • $\begingroup$ @GriffinEvo , I get your point...but what if I already know that the answer provided is correct??? $\endgroup$
    – souvik bhattacharya
    Commented Nov 19, 2014 at 14:57
  • $\begingroup$ ok..I get it..it's for greater good... $\endgroup$
    – souvik bhattacharya
    Commented Nov 19, 2014 at 15:04
  • $\begingroup$ @griffinEvo: :) $\endgroup$
    – Jaychandran
    Commented Nov 20, 2014 at 9:03

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