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FORENSIC ENTOMOLOGYFORENSIC ENTOMOLOGY

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

arrive at a decomposing body in a arrive at a decomposing body in a particular order and then complete their particular order and then complete their life cycle based on the surrounding life cycle based on the surrounding temperature. By collecting and studying temperature. By collecting and studying the types of insects found on a body, a the types of insects found on a body, a forensic entomologist can predict the time forensic entomologist can predict the time of death. of death.

““When one biological clock stops, others When one biological clock stops, others begin.”begin.”

--Neal Haskell, reknown forensic entomologist--Neal Haskell, reknown forensic entomologist

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HISTORICALLYHISTORICALLY

1235 A.D., a Chinese death 1235 A.D., a Chinese death investigator named 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 It contained one of the 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 There were no suspects, so the suspects, so the investigator had all the investigator had all the men of the village men of the village stand in a line with stand in a line with their sickles on the their sickles on the ground in front of ground in front of them. Flies landed on them. Flies landed on only one sickle--the only one sickle--the one, that although one, that although cleaned, still had cleaned, still had enough blood to 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 of Species that Feed on

Dead OrganismsDead Organisms Necrophages - feed directly on the corpseNecrophages - feed directly on the corpse

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

Predators and Parasites – attracted to Predators and Parasites – 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 of Species that Feed on

Dead OrganismsDead Organisms Species that feed on both the body and other Species that feed on both the body and other

arthropodsarthropods AntsAnts WaspsWasps Some beetlesSome beetles

Arthropods that use the corpse as an extension of Arthropods that use the corpse as an extension of their normal habitattheir 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 BlowflyThe Blowfly

Blowflies are one of the most common species on Blowflies are one of the most common species on dead bodies.dead 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 laying They feed on any blood or fluids and then start laying eggs in and around the natural body cavities. The eggs in and around the natural body cavities. The female can lay up to 250 eggs at one time.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 The eggs hatch within 23 hours. The maggots begin feeding on fluids leaking maggots begin feeding on fluids leaking form the body. Later they enter openings form the body. Later they enter openings on the body and feed on tissues.on the body and feed on tissues.

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

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

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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

Carrion Beetle--Silphidae (Nicrophorus sp.)

Rove Beetle--Staphylinidae (Lathrobium sp.)

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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 determined largely by estimating the age of the maggots at the time the age of the maggots at the time the corpse is discovered.corpse is discovered.

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

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LarvaLarva

Larva hatch from the Larva hatch from the eggs and increase in eggs and increase in size by growth steps size by growth steps called instars. called instars. Eventually the larva Eventually the larva migrate from the migrate from the corpse and develop corpse and develop into an inactive pupal into an inactive pupal stage. During this stage. During this time, the adult insect time, the adult insect develops internally.develops internally.Two larval instars.

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The Pupa and Adult FlyThe Pupa and Adult Fly

Once the maggot have Once the maggot have finished feeding, they finished feeding, they will pupate. During this will pupate. During this process the maggot process the maggot creates a hard brown creates a hard brown shell around itself. shell around itself.

Inside of the shell, the Inside of the shell, the maggot turns into an maggot turns into an adult fly. When the fly adult fly. When the fly emerges the shell is emerges the shell is left behind and 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

Factors such as weather, temperature, heat Factors such as weather, temperature, heat generated from the maggot mass, clothing generated from the maggot mass, clothing and wounds will affect the growth of the and wounds will affect the growth of the maggots.maggots.

Colder temperatures slow the growth of the Colder temperatures slow the growth of the maggots.maggots.

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

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Stages of A Pig Stages of A Pig DecompositionDecomposition

Complete metamorphosisComplete metamorphosis

involves developmentinvolves development

from egg to larva tofrom egg to larva to

pupa to adult. The pigpupa to adult. The pig

ear in the diagram to theear in the diagram to the

right shows a layer ofright shows a layer of

what looks like a whitewhat looks like a white

crust. These are the flycrust. These are the fly

eggs. 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 Procedures

In 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 Place them in boiling water to stretch them water to stretch them out and fix them. out and fix them. Then place the Then place the maggots into a vial of maggots into a vial of alcohol with a label alcohol with a label containing the date, containing the date, time, case #, location time, case #, location and collector. and collector.

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Live SamplingLive Sampling“Maggot Motels”“Maggot Motels”

Obtain a styrofoam container with a lid. Use sand Obtain a styrofoam container with a lid. Use sand or vermiculite for the bottom substrate. Place or vermiculite for the bottom substrate. Place aluminum foil with beef or pork liver for food on aluminum foil with beef or pork liver for food on top of the substrate. Collect 10 to 15 live top of the substrate. Collect 10 to 15 live maggots of varying sizes and drop them onto the maggots of varying sizes and drop them onto the foil. (You may also harvest and develop eggs in foil. (You may also harvest and develop eggs in the “motel”.) Close the foil around them and the “motel”.) Close the foil around them and allow to develop into pupae and then into adults. allow to develop into pupae and then into adults. THEY MUST BE ADULTS IN ORDER TO THEY MUST BE ADULTS IN ORDER TO IDENTIFY THE SPECIES.IDENTIFY THE SPECIES.

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More Maggot InformationMore Maggot Information

Maggots collected Maggots collected from a dead body from a dead body can be ground in a can be ground in a blender and tested blender and tested for any toxins for any toxins present in the body present in the body at the time of death. at the time of death. When the maggots When the maggots feed on the dead feed on the dead tissue, they ingest tissue, they ingest these toxins.these toxins.

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Maggot TherapyMaggot Therapy

The medical field The medical field uses maggots to uses maggots to eat dead and eat dead and decaying flesh on decaying flesh on wounds. This wounds. This allows the wound allows the wound to heal sooner, but to heal sooner, but many people still many people still find this disturbing!find this disturbing!