Decomposition is the process whereby bodily tissues are broken down into smaller molecules after death.
The physical and chemical properties observed during decay are categorized into five stages:
(1) fresh, (2) putrefaction, (3) black putrefaction, (4) butyric fermentation, and (5) dry decay.
[1] Seconds after death, insects are attracted to a body for food and to lay eggs in natural openings
and orifices of the body. This process of decomposition best describes the relationship between insect
colonization and the availability of different food sources throughout decay. The presence or absence of
a particular insect, location on the body, and food source, can help determine forensically pertinent
information about the body. Insects can provide significant insight to the manner of death, movement of
the corpse from one site to another, and length of the postmortem interval.[2]

A decaying carcass provides "a temporarily, rapidly changing resource which supports a large, dynamic arthropod community".
" Fresh Fresh stage The fresh stage is the first phase of decomposition that begins approximately four minutes
after death and lasts around three days until putrefaction. Autolysis initiates decay as digestive enzymes in
the body begin to break down nearby cell membranes and digest the internal organs. The acidity in the body also
increases due to lack of oxygen in tissues. The liver, which has high enzyme content, releases nutrient-rich fluids
into the body.[3] At this time, the body has little to no odor, the skin is quickly turning pale (pallor mortis)
and showing signs of livor mortis. The body loses heat until it reaches ambient temperature, known as algor mortis.
After several hours, fibers in the muscles of the body begin to bind together and stiffen. This is known as rigor mortis
and is first seen in the smaller muscles of the body like the face.[4] Insects will feed between the muscle during
rigor mortis because of the lactic acid produced from the breakdown of the muscle.[5]

The first necrophages observed on the body after death are the Calliphorid flies. The female green bottle fly
(Lucilia cuprina in the United States) is generally the first to colonize the body; the second is the
Hairy Maggot Blowfly, Chrysomya rufifacies.[6] Other fly families generally present during this stage are
Sarcophagidae, Piophilidae, and Muscidae.[7]

Predators of both immature and adult flies are prevalent at the beginning stages of decomposition.
These are important factors to consider when determining the insect colonization time.[7] Chrysomya rufifacies,
the second fly to colonize, facultatively predates on fly larvae in its second and third larval instar.
Saprinus pennsylvanicus, is a predaceous beetle in the United States that feeds on the early fly larvae.[8]
Parasitic wasps, fire ants, and other insects also predate on fly larvae. The parasitic wasps (such as the Chalcidae)
use the flies' pupae as a nest for their eggs; upon hatching, the wasp larvae feed on the host maggots or pupae.
Once the wasp larvae have killed the host, they use the fly remains to pupate into mature wasps.[1]

Putrefaction Following initial decay, approximately 4 to 10 days after death, the body begins the second stage
of decay called putrefaction. During putrefaction, bacteria and other microorganisms continue to anaerobically
metabolize the soft tissues of the body. This breakdown of tissue releases gases into the body and causes an
increased internal pressure, which results in a bloated corpse. These gases commonly consist of hydrogen sulfide,
carbon dioxide, methane, cadaverine, ammonia, sulfur dioxide, hydrogen, and putrescine.[3] According to Arpad Vass,
a greenish discoloration of skin due to the formation of sulfhaemoglobin in settled blood often signals the onset
of the putrefaction stage. As a result of the gas accumulation and the progression of decay, the corpse begins
to emit a smell. This smell is a putrid odor that tends to attract an increasing number and various species of
flies, beetles, and other arthropods.

During putrefaction, maggot habitation begins as flies continue to arrive and oviposit in the orifices and natural
openings of the corpse. Moreover, the first blowflies that arrived on the corpse during initial decay, have produced
larva that are in their first and second instars.[6] Clown beetles from the family Histeridae such as Hister
quadrinotatus and Hister seqkovi in the United States are also attracted during the bloat stage and can be found
underneath the decaying body.[8]

Black putrefaction Black putrefaction Black putrefaction, also known as active decay, happens about 10 to 25 days
after death.[7] A good indicator of black putrefaction is a strong odor and black coloration of the corpse.
The bloating begins to subside as the skin starts to peel back and break from the large amount of gas and fluids
produced. This makes the body appear flat. The breaking of the skin allows insects and other consumers better access
to the inside of the body. This open access to the inside of the body cavity aids in increasing the rate at which
viscera and other soft tissue decay.[9] Any remaining flesh still on the body has a soft creamy consistency.[3]
The nails on the fingers and toes of the body will readily disconnect.

Saponification is a processes that can slow down the rate of decay and lengthen the putrefaction process for years.
This process has also been called adipocere or grave wax. In humid, warm conditions, saponification may be seen on the
body in the form of an oily, waxy yellowish-white substance. This process occurs in the fats of animals and humans when
ester bonds, such as those in triglycerides, are exposed to a chemical base. In this case, water from moisture in the
environment acts as the chemical base and breaks the ester bonds of triglycerides of fat deposits.[10] When these bonds
break, fatty acids are released, which can form new bonds. What these free fatty acids bond to can influence the rate
of decay and the characteristics of the waxy substance formed.[3] This is aided by putrefactive bacteria, such as
Clostridium perfringens, to help make fat turn into a soapy substance.[11]

At this stage, the maggot mass starts to decrease as most of the maggots have reached their third molt and will start
to leave the body in order to pupate in the soil.[4] These maggots may live along side the larvae and adults of carrion
beetles (family Silphidae) and the skin beetles (family Dermestidae).[1] In the United States, types of carrion beetles
seen on the body may include Thanatophilus lapponicous, Necrophila americana, Oiceoptoma rugulosum and the burying beetle
Nicrophorus tomentosus.[8] Beetles usually make up the most of the population of insects on the body during black
putrefaction. This beetle mass can vary in the types of families, making it hard to designate a certain beetle family
to this stage of decay.[12] Parasitic wasps continue to prey on these maggots and many generations of mites feed on
the fluids let out by the body.[1]

Butyric fermentation Butyric fermentation is the name of the fourth stage of decomposition. This fermentation process
usually starts around 20-25 days after death. The body has finished flattening out from the previous putrefaction stage
and the flesh and fluids on the body are slowly drying up. Butyric acid produces a distinct smell which is a component
in breaking down the fluids in the body. This progression attracts different species of fauna to the carrion.[1]

Maggots and other insects that feed on soft flesh are unable to feed due to the drying out of the body; beetles and other
insects with similar chewing mouth appendages are able to crush and chew the tougher segments of the dead body. At this
time, most of the beetles are in the larval stage. Other insects such as cheese skippers and some parasitic wasps are
also present.[1] Hide Beetles from the family Trogidae and Carcass Beetles from the family Dermestidae are among the last
beetles and generally the most common beetles seen during this fermentation period. The Hide Beetles as well as the
Carcass Beetles are not predacious and are found on the tougher portions of the body such as bone and ligaments.[8]
Also, they are the only beetles that are capable of using an enzyme to break down proteins such as keratin.
The cheese fly from the family Piophilidae, is attracted to the smell produced by butyric acid.[1]

Dry decay Dry decay The final stage in animal decomposition is dry decay. Dry decay begins between 25 and 50 days
after death and can last up to a year. The only remnants of the body are dry skin, hair, and bones.
Mummification occurs when dehydrated tissues lack the nutritional value to be broken down by other means.
This is observed in dry heat or low humidity environments and can last for decades.[3] The bones go through a
process termed diagenesis that changes the organic to inorganic constituent ratio within the bones.[7] Any odor
exuding from the body at this point is merely the natural flora and fauna associated with the area.[13]

The fauna seen at this stage is limited. Bacteria feed on the hair and skin of the body, attracting many mites.
Certain tineid moths also feed on the remaining hair.[3] Silphidae, a family of carrion beetles, may still be present
during this stage. They typically arrive early in decomposition and stay until dry decay feeding on the larvae of other
insects. Beetles of the family Nitidulidae can also be seen inhabiting the body.[8] The normal soil fauna of the
environment will begin to return during this stage.[14]

Mummification Factors affecting decomposition Main article: Environmental effects on forensic entomology Understanding
how a corpse decomposes and the factors that may alter the rate of decay is extremely important for evidence in death
investigations. Campobasso, Vella, and Introna consider the factors that may inhibit or favor the colonization of insects
to be vitally important when determining the time of insect colonization.[13]

Temperature and climate
Low temperatures generally slow down the activity of blow-flies and their colonization of a body. Higher temperatures in
the summer favor large maggot masses on the carrion. Dry and windy environments can dehydrate a corpse, leading to
mummification. Dryness causes cessation in bacterial growth since there are no nutrients present to feed on.

Access
Access to the body can limit which insects can get to the body in order to feed and lay eggs. In the United States,
corpses found in brightly lit areas are generally inhabited by Lucilia illustris. This is in contrast to Phormia regina,
which prefers more shaded areas. Darkness, cold, and rain limit the amount of insects that would otherwise colonize the
body. A submerged corpse can vary in temperature and is colonized by very few terrestrial insects. Fish, crustaceans,
aquatic insects and bacteria would be the likely fauna in this case. Bodies that have been buried are harder to get to
than freely available bodies which limits the availability of certain insects to colonize. The Coffin fly Megaselia
scalaris is one of the few fly species seen on buried bodies because it has the ability to dig up to six feet
underground to reach a body and oviposit.

Reduction and cause of death
Scavengers and carnivores such as wolves, dogs, cats, beetles, and other insects feeding on the remains of a carcass
can make determining the time of insect colonization much harder. This is because the decomposition process has been
interrupted by factors that may speed up decomposition. Corpses with open wounds, whether pre or post mortem,
tend to decompose faster due to easier insect access. The cause of death likewise can leave openings in the body
that allow insects and bacteria access to the inside body cavities in earlier stages of decay. Flies oviposit eggs
inside natural openings and wounds that may become exaggerated when the eggs hatch and the larvae begin feeding.

Clothing and pesticides
Wraps, garments, and clothing have shown to effect the rate of decomposition because the corpse is covered by some type
of barrier. Wraps, such as tight fighting tarps can advance the stages of decay during warm weather when the body is
outside. However, loose fitting coverings that are open on the ends may aid colonization of certain insect species and
keep the insects protected from the outside environment. This boost in colonization can lead to faster decomposition.
Clothing also provides a protective barrier between the body and insects that can delay stages of decomposition.
For instance, if a corpse is wearing a heavy jacket, this can slow down decomposition in that particular area and
insects will colonize elsewhere. Bodies that are covered in pesticides or in an area surrounded in pesticides may
be slow to have insect colonization. The absence of insects feeding on the body would slow down the rate of decomposition.

Percent body fat of corpse
More fat on the body allows for faster decomposition. This is due to the composition of fat, which is high in water
content. Larger corpses with higher percent body fat also tend to retain heat much longer than corpses with less body fat.
Higher temperatures favor the reproduction of bacteria inside high nutrient areas of the liver and other organs.

Drugs
On occasion, drugs that are present in the body at death can also affect how fast insects break down the corpse.
Development of these insects can be sped up by cocaine and slowed down by drugs containing arsenic.[13][9]
Current research New research in the related field entomotoxicology is currently studying the effects of drugs on the
development of insects who have fed on the decomposing tissue of a drug user. The effects of drugs and toxins on insect
development are proving to be an important factor when determining the insect colonization time. It has been shown that
cocaine use can accelerate the development of maggots. In one case, Lucilia sericata larvae that fed in the nasal cavity
of a cocaine abuser, grew over 8 mm longer than larvae of the same generation found elsewhere on the body.[15] Other
researchers in entomotoxicology are developing techniques to detect and measure drug levels in older fly pupae.
This research is useful for determining cause of death for bodies that are found during later stages of decay.
To this date, bromazepam, levomepromazine, malathion, phenobarbital, trazolam, oxazepam, alimemazine, clomipramine,
morphine, mercury, and copper have been recovered from maggots.[2]

Conclusion Understanding the stages of decomposition, the colonization of insects, and factors that may affect decomposition
and colonization are key in determining forensically important information about the body. Different insects colonize the
body throughout the stages of decomposition. These stages are categorized into fresh, putrefaction, black putrefaction,
butyric fermentation, and dry decay. Identifying which insect is present can be useful in determining what stage of decay
the body is in. Some insects are only found in certain regions and this information can help determine if a body has been
moved by the type of maggots feeding on the body. The environment surrounding the body is also very important to consider
when using insect evidence. Insects, such as the coffin fly Megaselia scalaris, are nearly always found on bodies that
have been buried. Using evidence that is very species specific can reveal a great deal of information about a body.

Adipocere Adipocere (pronounced /?ĉd?po?si?r/), also known as corpse, grave or mortuary wax, is a wax-like organic substance
formed by the anaerobic bacterial hydrolysis of fat in tissue, such as body fat in corpses. In its formation, putrefaction
is replaced by a permanent firm cast of fatty tissues, internal organs and the face.

History Adipocere was first described by Sir Thomas Browne in his discourse Hydriotaphia, Urn Burial (1658):[1]
In a Hydropicall body ten years buried in a Church-yard, we met with a fat concretion, where the nitre of the Earth,
and the salt and lixivious liquor of the body, had coagulated large lumps of fat, into the consistence of the hardest
castle-soap: wherof part remaineth with us. The chemical process of adipocere formation, saponification, came to be
understood in the 17th century when microscopes became widely available.[1]

Augustus Granville is believed to have somewhat unwittingly made candles from the adipocere of a mummy and used them to
light the public lecture he gave to report on the mummy's dissection.[2]

Appearance Adipocere is a crumbly, waxy, water-insoluble material consisting mostly of saturated fatty acids.
Depending on whether it was formed from white or brown body fat, adipocere is grayish white or tan in color.[1]
In corpses, the firm cast of adipocere allows some estimation of body shape and facial features, and injuries are
often well-preserved.[1] An example of such a corpse is available at the Mütter Museum in Philadelphia, Pennsylvania.
Formation The transformation of fats into adipocere occurs best in the absence of oxygen in a cold and humid environment,
such as in wet ground or mud at the bottom of a lake or a sealed casket, and it can occur with both embalmed and untreated
bodies. Adipocere formation begins within a month of death, and in the absence of air it can persist for centuries.[3]
An exposed, infested body or a body in a warm environment is unlikely to form deposits of adipocere.

Corpses of women, infants and overweight persons are particularly prone to adipocere transformation because they contain
more body fat.[1] In forensic science, the utility of adipocere formation to estimate the postmortem interval is limited
because the speed of the process is temperature-dependent. It is accelerated by warmth, but temperature extremes impede it.[1]

When someone's heart stops pumping blood around their body, the tissues and cells are deprived of oxygen and rapidly
begin to die.
But different cells die at different rates. So, for example, brain cells die within three to seven minutes,
while skin cells can be taken from a dead body for up to 24 hours after death and still grow normally in a laboratory
culture.
But contrary to folklore, this doesn't mean that hair and nails continue to grow after death, although shrinkage of
the skin can make it seem this way.
From this point on, nature is very efficient at breaking down human corpses. Decomposition is well under way by the
time burial or cremation occurs. However, the exact rate of decomposition depends to some extent on environmental
conditions.

Decomposition in the air is twice as fast as when the body is under water and four times as fast as underground.
Corpses are preserved longer when buried deeper, as long as the ground isn't waterlogged.
The intestines are packed with millions of micro-organisms that don't die with the person. These organisms start to
break down the dead cells of the intestines, while some, especially bacteria called clostridia and coliforms,
start to invade other parts of the body.
At the same time the body undergoes its own intrinsic breakdown under the action of enzymes and other chemicals which
have been released by the dead cells. The pancreas, for example, is usually packed with digestive enzymes, and so rapidly
digests itself
The decomposing tissues release green substances and gas, which make the skin green/blue and blistered, starting on
the abdomen. The front of the body swells, the tongue may protrude, and fluid from the lungs oozes out of the mouth
and nostrils.
This unpleasant sight is added to by a terrible smell as gases such as hydrogen sulphide (rotten egg smell), methane
and traces of mercaptans are released. This stage is reached in temperate countries after about four to six days,
much faster in the tropics and slower in cold or dry conditions.
oh and alsoA corpse left above ground is then rapidly broken down by insects and animals, including bluebottles and
carrion fly maggots, followed by beetles, ants and wasps.
In the tropics, a corpse can become a moving mass of maggots within 24 hours.
If there are no animals to destroy the body, hair, nails and teeth become detached within a few weeks, and after a
month or so the tissues become liquefied and the main body cavities burst open.
Burial in a coffin slows the process The whole process is generally slower in a coffin, and the body may remain identifiable for many months.
Some tissues, such as tendons and ligaments, are more resistant to decomposition, while the uterus and prostate
glands may last several months.
But within a year all that is usually left is the skeleton and teeth, with traces of the tissues on them
- it takes 40 to 50 years for the bones to become dry and brittle in a coffin. In soil of neutral acidity,
bones may last for hundreds of years, while acid peaty soil gradually dissolves the bones.