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FORENSIC ENTOMOLOGYFORENSIC ENTOMOLOGY

“When one biological clock stops, others begin.”--Neal Haskell, reknown forensic entomologist

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Entomology Entomology Entomology is the study of insects. Entomology is the study of insects.

Insects arrive at a decomposing body in a Insects arrive at a decomposing body in a particular order and then complete their life particular order and then complete their life cycle based on the surrounding temperature. cycle based on the surrounding temperature.

By collecting and studying the types of insects By collecting and studying the types of insects found on a body, a forensic entomologist can found on a body, a forensic entomologist can predict the time of death. predict the time of death.

A forensic entomologist’s job may include:

Identification of insects at various stages of their life cycle, Identification of insects at various stages of their life cycle, such as eggs, larva, and adults.such as eggs, larva, and adults.

Collection and preservation of insects as evidence.Collection and preservation of insects as evidence.

Determining an estimate for the Determining an estimate for the postmortem intervalpostmortem interval or or PMI PMI (the time between death and the discovery of the body) (the time between death and the discovery of the body) using using factors such as insect evidence, weather conditions, location factors such as insect evidence, weather conditions, location and condition of the body, etc.and condition of the body, etc.

Testifying in court to explain insect-related evidence found at Testifying in court to explain insect-related evidence found at a crime scene.a crime scene.

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HISTORICALLYHISTORICALLY 1235 A.D., a Chinese 1235 A.D., a Chinese

death investigator named death investigator named Sung Tz’u wrote a book Sung Tz’u wrote a book entitled entitled The Washing The Washing Away of Wrongs. Away of Wrongs.

It contained one of the It contained one of the first accounts of the use first accounts of the use of insects as forensic of insects as forensic evidence. A murder, in evidence. A murder, in which a sickle was used, which a sickle was used, occurred in a Chinese occurred in a Chinese village. village.

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HISTORICALLY (cont.)HISTORICALLY (cont.) There were no suspects, There were no suspects,

so the investigator had so the investigator had all the men of the village all the men of the village stand in a line with their stand in a line with their sickles on the ground in sickles on the ground in front of them. front of them.

Flies landed on only one Flies landed on only one sickle--the one, that sickle--the one, that although cleaned, still although cleaned, still had enough blood to had enough blood to attract the flies. The attract the flies. The owner then confessed.owner then confessed.

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Four Main Types Four Main Types of Species that Feed on Dead of Species that Feed on Dead

OrganismsOrganisms NecrophagesNecrophages - feed directly on the corpse - feed directly on the corpse

Flies (Diptera)Flies (Diptera) Beetles (Coleoptera)Beetles (Coleoptera)

Predators and Parasites Predators and Parasites – attracted to – attracted to organisms that are already feeding on the organisms that are already feeding on the bodybody Burying beetles (family Silphidae)Burying beetles (family Silphidae) Rove beetles (family Staphylinidae)Rove beetles (family Staphylinidae) Hister beetles (family Histeridae)Hister beetles (family Histeridae) Ants, bees, and wasps (Order of Hymenoptera)Ants, bees, and wasps (Order of Hymenoptera)

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Four Main Types Four Main Types of Species that Feed on Dead of Species that Feed on Dead

OrganismsOrganisms Species that feed on both the body and Species that feed on both the body and

other arthropodsother arthropods AntsAnts WaspsWasps Some beetlesSome beetles

Arthropods that use the corpse as an Arthropods that use the corpse as an extension of their normal habitatextension of their normal habitat Hunting spidersHunting spiders

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The First SpeciesThe First Species Flies are able to Flies are able to

detect the smell of detect the smell of decomposition decomposition before humans. before humans.

When a dead body When a dead body is placed outside a is placed outside a blowfly will blowfly will generally appear generally appear within ten minutes.within ten minutes.

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The Blowfly The Blowfly one of the most common species on dead one of the most common species on dead

bodies.bodies. Blowflies have a shiny, metallic color so they are Blowflies have a shiny, metallic color so they are

often called blue-bottle or green-bottle flies.often called blue-bottle or green-bottle flies.

They feed on any blood or fluids and then start They feed on any blood or fluids and then start laying eggs in and around the natural body cavities. laying eggs in and around the natural body cavities.

The female can lay up to 250 eggs at one time.The female can lay up to 250 eggs at one time.

Once the food source is exhausted, they will prey on Once the food source is exhausted, they will prey on other species in the same genus (other species in the same genus (ChrysomyaChrysomya))

Therefore, they act as both necrophages and Therefore, they act as both necrophages and predators.predators.

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The BlowflyThe Blowfly The eggs hatch within 23 hours. The maggots The eggs hatch within 23 hours. The maggots

begin feeding on fluids leaking form the body. begin feeding on fluids leaking form the body. Later they enter openings on the body and feed Later they enter openings on the body and feed on tissues.on tissues.

Other species of flies will begin to arrive and Other species of flies will begin to arrive and there will be competition for access to the corpse.there will be competition for access to the corpse.

The maggots are also a source of food for other The maggots are also a source of food for other insects.insects.

The maggots become a The maggots become a source of food for other source of food for other insects such as Beetlesinsects such as Beetles

Clown Beetles (Histeridae)

Predator of fly eggs

Rove Beetles (Staphylinidae)

Predator of fly eggs

Carrion Beetle (Necrophila americana,[1]

formerly Silpha americana)Feeds on the flesh and preys on

the fly larva

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Minimum Time Since Minimum Time Since DeathDeath

The minimum time since death is The minimum time since death is determined largely by estimating the age of determined largely by estimating the age of the maggots at the time the corpse is the maggots at the time the corpse is discovered.discovered.

The fundamental assumption is that the The fundamental assumption is that the person has not been dead longer than it took person has not been dead longer than it took for the flies to arrive, lay eggs and maggots for the flies to arrive, lay eggs and maggots hatch and develop. Therefore, the oldest hatch and develop. Therefore, the oldest maggot determines the minimum time since maggot determines the minimum time since death.death.

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LarvaLarva Larva hatch from the eggs Larva hatch from the eggs

and increase in size by and increase in size by growth steps called growth steps called instars. instars.

Eventually the larva Eventually the larva migrate from the corpse migrate from the corpse and develop into an and develop into an inactive pupal stage. inactive pupal stage.

During this time, the adult During this time, the adult insect develops internally.insect develops internally.Two larval instars.

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The Pupa and Adult FlyThe Pupa and Adult Fly Once the maggot have finished Once the maggot have finished

feeding, they will feeding, they will pupatepupate. .

During this process the maggot During this process the maggot creates a hard brown shell creates a hard brown shell around itself. around itself.

Inside of the shell, the maggot Inside of the shell, the maggot turns into an adult fly.turns into an adult fly.

When the fly emerges the When the fly emerges the shell is left behind and shell is left behind and becomes another clue.becomes another clue.

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The Cycle of a Blowfly shows the time The Cycle of a Blowfly shows the time frame that is used to determine the frame that is used to determine the

minimum time since death.minimum time since death.

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Factors that affect maggot Factors that affect maggot growthgrowth

Growth of maggots affected by factors such as:Growth of maggots affected by factors such as: weather/precipitationweather/precipitation temperature of air and ground surface - colder temperature of air and ground surface - colder

temperatures slow the growth of the maggots.temperatures slow the growth of the maggots. heat generated by the maggot mass heat generated by the maggot mass clothing clothing type of woundstype of wounds

If drugs are present in the body at the time of If drugs are present in the body at the time of death, these toxins will also affect the rate of death, these toxins will also affect the rate of development.development.

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Pig Decomposition Pig Decomposition Pig decomposition is Pig decomposition is

almost identical to almost identical to human decomposition. human decomposition.

Therefore, pigs are Therefore, pigs are used in forensic used in forensic entomological studies entomological studies in order to better in order to better understand what understand what happens when a human happens when a human decomposes.decomposes.

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Stages of A Pig Stages of A Pig DecompositionDecomposition

Complete Complete metamorphosis metamorphosis involves development involves development from egg to larva to from egg to larva to pupa to adult. pupa to adult.

The pig ear in the The pig ear in the diagram to the right diagram to the right shows a layer of what shows a layer of what looks like a white crust. looks like a white crust. These are the fly eggs. These are the fly eggs.

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Pig DecompositionPig Decomposition

One day old dead pig showing signs of skin changes and bloating.

(Picture taken on June 20th, 2002)

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Pig DecompositionPig Decomposition

Advanced stages are seen on this one week old dead pig. As the larva develop they migrate from the body and develop

into pupa.

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Collection ProceduresCollection ProceduresIn order to study the maggots, pupa In order to study the maggots, pupa

and flies, they must be collected. and flies, they must be collected. Collections may be done in three Collections may be done in three differnet ways:differnet ways: AerialAerial HandHand Live SamplingLive Sampling

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Aerial CollectionAerial CollectionUse a net and sweep it Use a net and sweep it

back and forth over the back and forth over the decomposing body. decomposing body. Place them in a large jar Place them in a large jar with ethyl acetate. After with ethyl acetate. After a few seconds, use a a few seconds, use a funnel to move dead funnel to move dead flies into a vial of 75% flies into a vial of 75% ethyl alcohol with a label ethyl alcohol with a label of the date, time, case of the date, time, case #, location, sample type #, location, sample type and collector. and collector.

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Hand Hand CollectionCollection

Collect a variety of Collect a variety of maggots with forceps.maggots with forceps.

Place them in boiling water Place them in boiling water

to stretch them out and fix to stretch them out and fix them. them.

Then place the maggots Then place the maggots into a vial of alcohol with a into a vial of alcohol with a label containing the date, label containing the date, time, case #, location and time, case #, location and collector. collector.

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Live SamplingLive Sampling“Maggot Motels”“Maggot Motels”

Obtain a styrofoam container with a lid. Obtain a styrofoam container with a lid. Use sand or vermiculite for the bottom substrate. Use sand or vermiculite for the bottom substrate. Place aluminum foil with beef or pork liver for food on Place aluminum foil with beef or pork liver for food on

top of the substrate. top of the substrate. Collect 10 to 15 live maggots of varying sizes and drop Collect 10 to 15 live maggots of varying sizes and drop

them onto the foil. (You may also harvest and develop them onto the foil. (You may also harvest and develop eggs in the “motel”.) eggs in the “motel”.)

Close the foil around them and allow to develop into Close the foil around them and allow to develop into pupae and then into adults. pupae and then into adults. THEY MUST BE ADULTS THEY MUST BE ADULTS IN ORDER TO IDENTIFY THE SPECIES.IN ORDER TO IDENTIFY THE SPECIES.

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More Maggot InformationMore Maggot Information When the maggots feed When the maggots feed

on the dead tissue, they on the dead tissue, they ingest any toxins ingest any toxins present.present.

Maggots collected from Maggots collected from a dead body can be a dead body can be ground in a blender and ground in a blender and tested for any toxins tested for any toxins present in the body at present in the body at the time of death.the time of death.

READ ARTICLE READ ARTICLE Next Next

Medical MaggotsMedical Maggots

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Maggot TherapyMaggot Therapy The medical field The medical field

uses maggots to eat uses maggots to eat dead and decaying dead and decaying flesh on wounds. flesh on wounds.

This allows the This allows the wound to heal wound to heal sooner, but many sooner, but many people still find this people still find this disturbing!disturbing!