Forensic entomology —the study of how insects interact with dead bodies—can help law enforcement and lawyers in criminal investigations, and maggots are a big part of that. Hundreds of insect species can be involved in breaking down a dead body, but flies and beetles are the "major players," he said.
When an animal dies, microbes begin to break down its tissues and produce gases, Tomberlin explained. This is what makes corpses bloat. Then come the insects. Blowflies , flesh flies , and black soldier flies are typical species found on vertebrate remains. The flies home in on moist cavities like the mouth, nose, and eyes to lay their eggs. The young that hatch out are the maggots, which proceed to eat their way through the surrounding soft tissue. Different fly species have different dietary requirements, Tomberlin explained.
The black soldier fly maggots in the video above are omnivorous, meaning they can eat a wide variety of foods, including the chicken tacos provided as a demonstration. Scavengers such as raccoons, coyotes, and possums will also consume the remains.
In the southern U. The forensic entomologist studies flies and maggots in his laboratory to figure out just what factors influence when the insects colonize human or animal remains. A better understanding of colonization times would "allow forensic entomologists to better predict the actual time of death of the person in question. This may be due partly to differences in the composition of the microbiome of each cadaver, or it might be caused by differences in the time elapsed since death.
An earlier study of decomposing mice revealed that although the microbiome changes dramatically after death, it does so in a consistent and measurable way. The researchers were able to estimate time of death to within three days of a nearly two-month period. Javan's study suggests that this 'microbial clock' may be ticking within the decomposing human body, too.
It showed that the bacteria reached the liver about 20 hours after death and that it took them at least 58 hours to spread to all the organs from which samples were taken. Thus, after we die, our bacteria may spread through the body in a systematic way, and the timing with which they infiltrate first one internal organ and then another may provide a new way of estimating the amount of time that has elapsed since death.
One thing that does seem clear, however, is that a different composition of bacteria is associated with different stages of decomposition. Scattered among the pine trees in Huntsville, Texas, lie around half a dozen human cadavers in various stages of decay. The two most recently placed bodies are spread-eagled near the centre of the small enclosure with much of their loose, grey-blue mottled skin still intact, their ribcages and pelvic bones visible between slowly putrefying flesh.
A few metres away lies another, fully skeletonised, with its black, hardened skin clinging to the bones, as if it were wearing a shiny latex suit and skullcap. Further still, beyond other skeletal remains scattered by vultures, lies a third body within a wood and wire cage. It is nearing the end of the death cycle, partly mummified.
Several large, brown mushrooms grow from where an abdomen once was. For most of us the sight of a rotting corpse is at best unsettling and at worst repulsive and frightening, the stuff of nightmares.
Within it, a nine-acre plot of densely wooded land has been sealed off from the wider area and further subdivided, by foot-high green wire fences topped with barbed wire.
In late , SHSU researchers Sibyl Bucheli and Aaron Lynne and their colleagues placed two fresh cadavers here, and left them to decay under natural conditions. Once self-digestion is under way and bacteria have started to escape from the gastrointestinal tract, putrefaction begins.
This is molecular death — the breakdown of soft tissues even further, into gases, liquids and salts. It is already under way at the earlier stages of decomposition but really gets going when anaerobic bacteria get in on the act.
Putrefaction is associated with a marked shift from aerobic bacterial species, which require oxygen to grow, to anaerobic ones, which do not. These then feed on the body's tissues, fermenting the sugars in them to produce gaseous by-products such as methane, hydrogen sulphide and ammonia, which accumulate within the body, inflating or 'bloating' the abdomen and sometimes other body parts. This causes further discolouration of the body.
As damaged blood cells continue to leak from disintegrating vessels, anaerobic bacteria convert haemoglobin molecules, which once carried oxygen around the body, into sulfhaemoglobin. The presence of this molecule in settled blood gives skin the marbled, greenish-black appearance characteristic of a body undergoing active decomposition. As the gas pressure continues to build up inside the body, it causes blisters to appear all over the skin surface.
This is followed by loosening, and then 'slippage', of large sheets of skin, which remain barely attached to the deteriorating frame underneath. Eventually, the gases and liquefied tissues purge from the body, usually leaking from the anus and other orifices and frequently also leaking from ripped skin in other parts of the body. Sometimes, the pressure is so great that the abdomen bursts open.
Bloating is often used as a marker for the transition between early and later stages of decomposition, and another recent study shows that this transition is characterised by a distinct shift in the composition of cadaveric bacteria. Bucheli and Lynne took samples of bacteria from various parts of the bodies at the beginning and the end of the bloat stage.
They then extracted bacterial DNA from the samples and sequenced it. As an entomologist, Bucheli is mainly interested in the insects that colonise cadavers.
She regards a cadaver as a specialised habitat for various necrophagous or 'dead-eating' insect species, some of which see out their entire life cycle in, on and around the body. When a decomposing body starts to purge, it becomes fully exposed to its surroundings. At this stage, the cadaveric ecosystem really comes into its own: a 'hub' for microbes, insects and scavengers.
Two species closely linked with decomposition are blowflies and flesh flies and their larvae. Cadavers give off a foul, sickly-sweet odour, made up of a complex cocktail of volatile compounds that changes as decomposition progresses.
Blowflies detect the smell using specialised receptors on their antennae, then land on the cadaver and lay their eggs in orifices and open wounds. Each fly deposits around eggs that hatch within 24 hours, giving rise to small first-stage maggots.
These feed on the rotting flesh and then moult into larger maggots, which feed for several hours before moulting again. After feeding some more, these yet larger, and now fattened, maggots wriggle away from the body. Decomposition of a corpse is a continual process that can take from weeks to years, depending on the environment. Below we have divided the process into stages, which are characterised by particular physical conditions of the corpse and the presence of particular animals.
To illustrate the process of decomposition, we use the piglet as the model corpse. Piglets are used because a 40 kg pig resembles a human body in its fat distribution, cover of hair and ability to attract insects.
These factors make pigs the next best things to humans when it comes to understanding the process of decay of the human body. The pigs in this website are newborn piglets weighing about 1. Their bodies have been donated to science. Please note - this set of images contain strong graphic references and descriptions. A live pig is not outwardly decomposing, but its intestine contains a diversity of bacteria , protozoans and nematodes. Some of these micro-organisms are ready for a new life, should the pig die and lose its ability to keep them under control.
Get our monthly emails for amazing animals, research insights and museum events. Although the body shortly after death appears fresh from the outside, the bacteria that before death were feeding on the contents of the intestine begin to digest the intestine itself. They eventually break out of the intestine and start digesting the surrounding internal organs. The body's own digestive enzymes normally in the intestine also spread through the body, contributing to its decomposition.
On an even smaller scale, enzymes inside individual cells are released when the cell dies. These enzymes break down the cell and its connections with other cells. From the moment of death flies are attracted to bodies. Without the normal defences of a living animal, blowflies and house flies are able to lay eggs around wounds and natural body openings mouth, nose, eyes, anus, genitalia.
These eggs hatch and move into the body, often within 24 hours. The life cycle of a fly from egg to maggot to fly takes from two to three weeks. It can take considerably longer at low temperatures. Bacteria break down tissues and cells, releasing fluids into body cavities. They often respire in the absence of oxygen anaerobically and produce various gases including hydrogen sulphide, methane, cadaverine and putrescine as by-products. People might find these gases foul smelling, but they are very attractive to a variety of insects.
The build up of gas resulting from the intense activity of the multiplying bacteria , creates pressure within the body. This pressure inflates the body and forces fluids out of cells and blood vessels and into the body cavity. The young maggots move throughout the body, spreading bacteria , secreting digestive enzymes and tearing tissues with their mouth hooks.
They move as a maggot mass benefiting from communal heat and shared digestive secretions. The rate of decay increases, and the smells and body fluids that begin to eminate from the body attract more blowflies, flesh flies , beetles and mites.
The later-arriving flies and beetles are predators, feeding on maggots as well as the decaying flesh. They are joined by parasitoid wasps that lay their eggs inside maggots and later, inside pupae. The bloated body eventually collapses, leaving a flattened body whose flesh has a creamy consistency. The exposed parts of the body are black in colour and there is a very strong smell of decay. A large volume of body fluids drain from the body at this stage and seep into the surrounding soil.
Other insects and mites feed on this material. Therefore, it is extremely important to know whether masses are present. It is of less use in winter, unless its very mild, as there are no or very few insects present. This can be a limitation, but can also be an advantage as I can sometimes show that a victim found in spring was killed the previous fall if insect evidence is present.
DNA evidence is now being developed to speed up identification of immature specimens. However, other forensic experts would be able to determine whether or not the body has been frozen, and insect evidence will still determine time of exposure. However, most criminal burials are not very deep, as the aim is merely to conceal the body, and most insects will dig down to the body, particularly if there is blood soaked in the soil.
Therefore, insect evidence can still be used. We have an estensive database for buried bodies in B. A body part was found sealed in a garbage bag which had been tied securely at the top, but the remains were maggot-infested, and showed severe insect damage. The adult females had probably laid their eggs at the knot, and the minute first instar larvae had crawled in.
Insect succession varies from geographic region to region and the species and time of colonization must be developed for all areas using this type of evidence. Research has been conducted in British Columbia in a variety of habitats, seasons and geographic areas to develop a database for this Province. Drugs - the presence of drugs may affect the development of the insects. Work is planned to determine effects of common narcotics on insects in Canada. Forensic entomology is a very useful method of determining elapsed time since death after 72 h, and can be used earlier.
It is accurate to a day or less, or a range of days, and may be the only method available to determine elapsed time since death.
I have successfully defended this evidence in court many times. It is vital that the insects are collected properly and its accuracy depends on this and on suitable conditions for insects. GAIL S. Pager - 24h , office or home. Police case number Date Time. Date found Time found. Location found.
Officer in Charge tel. Collecting officer tel. Weather conditions at collection time rain and temp. Please describe. Ground body resting on. How deep? Body position. Stage of decomposition. General scene Are there any maggot masses very large no.
If so, how many , where , temp. Description of insect evidence - e. Samples :- collect from the body itself, and from the ground soil or carpet below and around the body. If on soil or loose material, the insects may be several centimetres down, and on any surface may be up to cm away from the body. Older maggots will crawl away from the body to pupate, so may be still maggots, or may be pupae, which are 5mm-1cm long, red-dark brown, and look somewhat like a chocolate rice crispy.
It is very important to know whether pupae or empty pupal cases are present and to collect them. They are quite delicate - do not preserve them. Only preserve maggots. Only some maggots should be preserved, at least half should be kept alive.
Sample If remains were refrigerated at morgue, and collection was performed at autopsy Time and date body entered the cooler Time and date body removed from cooler Exhibit no. Keep maggots and beetles adult or larvae separate.
Keep samples from different sites separate. Put live maggots in vial with very small air-holes, a piece of paper tissue, and some food, preferably beef liver about 1 cubic inch. Only put about large maggots in one container, up to small ones are O. Signature of Collector. V5A 1S6 Tel. The second method, that of using maggot age and development can give a date of death accurate to a day or less, or a range of days, and is used in the first few weeks after death.
Maggots are larvae or immature stages of Diptera or two-winged flies. The insects used in this method are those that arrive first on the corpse, that is, the Calliphoridae or blowflies. These flies are attracted to a corpse very soon after death. They lay their eggs on the corpse, usually in a wound, if present, or if not, then in any of the natural orifices. Their development follows a set, predictable, cycle. Other important information used to determine elapsed time since death include :- weather records from the nearest weather station, including temperature and precipitation the distance between the death site and the weather station This method of determining elapsed time since death using insect evidence can be demonstrated using an actual case.
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