Death and decays

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  • 1. Revision
    Unit 4
    Death and Decay
  • 2. Stages of succession on a dead body
    Anaerobic bacteria
    Parasitic wasps
    Cheese flies and coffin flies
    Carcass beetles, ham beetles and hide beetles
    Mites and moth larvae
  • 3.
  • 4. Stages of succession on a dead body
    Anaerobic bacteria (do not need oxygen and thrive in the lactic acid-rich environment of the muscles after death) are the first colonisers.
    These bacteria are found in small areas of a living body such as gut.
    After death these bacteria spread to other parts of the body as enzymes break down cells.
  • 5. FLIES
    These insects are extremely sensitive to the smell of dead organisms, and can arrive on a body within minutes of death.
    They are attracted to the moisture and smell around all the natural openings of the body, as well as any open wounds.
    At first, the main attraction of the body is as a site on which to lay eggs.
    The maggots hatch and immediately begin feeding on the tissues, breaking them down.
    Eventually the maggots pupate, turn into flies and immediately mate and start the cycle again.
    As the soft tissues of the body liquefy, adult flies can feed on this too.
  • 6. Beetles:
    Beetles also start to lay eggs on the carcass, as their larvae feed on maggots rather than eat the body itself.
    Parasitic Wasps:
    Parasitic wasps arrive to lay their eggs in the fly and beetle larvae.
    Gradually, as the body is digested it also dries out, which does not suit the early colonisers.
  • 7. Late Colonisers
    Different species such as the cheese flies and coffin flies move in.
    Eventually the body is too dry for maggots.
    A number of beetle species with strong, chewing mouth parts move in.
    These include carcass beetles, ham beetles and hide beetles, which feed on the remains of the muscles and the connective tissues.
    At the very end, mites and moth larvae will feed on the hair until only dry bones are left.
  • 8. Factors affecting decay
    The warmer the body the faster the rate of decay.
    Chemical reactions speed up as the temperature increases.
    A body kept in very cold conditions will decay slowly
    Buried bodies decompose slowly than bodies left in the open air
    This is because the body not available for flies and other decomposers found in the open air.
    Temperature of the underground will be lower and more stable.
    A body hidden in a house will decompose slower compared to one outside.
  • 9. Forensic Entomology : The study of insect life that are related to crime.
  • 10. Study of insects help forensic entomologists to estimate the time of death and even cause of death.
    If a body is found in the open field without any blowfly activity, the scientist will have an idea that it is a recent death (less than 24 hours, as the blowflies often find bodies within minutes of death)
    The flies lay their eggs around openings of the body.
    They also lay eggs around wounds in the body, and an abundance of larvae at locations of the body where normal openings are absent indicate wounds and thus cause of death.
  • 11. The time taken for the blowfly life cycle to be completed depends on the temperature.
    In colder weather the maggots grow more slowly.
  • 12. Forensic entomology
    Body discovered
    Eggs, maggots and pupae are collected
    Live specimens collected are allowed to grow (these are used for identification)
    Compare with standard lifecycle of flies at different temperatures
    Time of death calculated