Forensic Entomology

1
Forensic Entomology

• Also Included Maggot Therapy and Taxidermy

2
Forensic Entomology Relies Strongly on the
Following Ecological Concepts

• Developmental time is temperature dependant at
  the microhabitat level.
• Ecological succession A corpse will be invaded
  by a series of different species or insect groups
  over time. Each species or group changes the
  microenvironment through its activities which
  makes it attractive to new waves of organisms and
  so on.

3
Forensic Entomology is Involved With Arthropod
Involvement in Events Surrounding Felonies

• Violent Crimes
• murder, suicide and rape
• physical abuse
• contraband trafficking

4
The Most Common Application Relates to Death
Investigations

• Determining PMI postmortem interval
• Movement of the corpse
• Manner and cause of death
• Association of suspects with the death scene
• Detection of toxins or drugs through analysis of
  insect larvae

5
Estimates of PMI Using Insects May Be Based On

• Period of time for a given species to reach a
  particular stage of development
• Comparisons of assemblages of insect fauna on
  corpse at time of examination
• A combination of both above

6
Most Important Environmental Factors in Corpse
Decay

• Temperature
• Access by insects
• Depth of Burial
• Based on study of decay rates of 150 human
  corpses at U. of Tenn.

7
Rcological Roles of Insects in Decompositon

• Necrophages species feeding on corpse tissue
  mostly true flies and beetles age determination
  (larval instar) important for PMI
• Omnivores insects that feed both on the corpse
  and associated fauna ants, wasps and some
  beetles may alter rate of decomposition
• Parasites and Predators many beetles, true
  flies and wasps that attack immature flies
• Incidentals use the corpse as a resource
  extension springtails, spiders, centipedes, some
  mites

8
Five Stages of Human Decomposition Have Been
Recognized -1

• Fresh Stage (Days 1-2) From moment of death to
  first sign of bloating flesh flies, blow flies,
  ants eating fly eggs and predatory wasps

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Flesh Flies 2 Species
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Two Blowfly Species
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Blowfly Larvae
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House Flies on Dead Host
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Five Stages 2

• Bloated stage (Days 2-6) putrefaction begins
  gases produced by anaerobic bacteria
  considerable bloating seepage of fluids adult
  and larval blowflies attracted in large numbers
  to seepage soil fauna moves away due to wetness
  of earth ants and other species of flies prey on
  maggots

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Five Stages 3

• Decay Stage (Days 5-11) Abdominal wall is
  broken and carcass deflates adult flies begin to
  leave but great masses of maggots remain and
  feed carcass will begin to dry and beetles begin
  feeding on drier tissue flies start to pupate
  predatory beetles such as rove and hister beetles
  are attracted

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Pig Carcass Infested With Blowfly Maggots
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Hister Beetles Prey on Blowfly Larvae
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Rove Beetles 2 Species
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Five Stages 4

• Postdecay Stage (Days 10-25)
• in dry habitats - remains consist of dry skin,
  cartilage and bones site for dermestid beetles,
  histerids, fly pupae, immature and adult rove
  beetles
• in wet habitats large quantities of wet,
  viscous material (byproducts of decomposition)
  found in soil under the remains site for adult
  and immature moth flies, rove beetles

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Dermestid Beetles Adult and Larvae
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Five Stages 5

• Dry Stage (Days 25) Mainly bone and hair is
  all that remains odor is primarily that of soil
  and litter some dermestids, fly pupae, immature
  and adult rove beetles, normal soil fauna
  consisting of mites, etc. start to return this
  stage could last for several months to years

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Carrion Beetles 2 Species
22
Female Carrion Beetle and Kangaroo Rat
Rat will be completely buried and eggs laid upon
it.
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Barriers to Decomposition and Irregular
Decomposition

• Physical soil, water, caskets, antermortem and
  postmotem injuries
• Chemical embalming agent, insecticides, lime,
  etc.
• Climatic heat, cold, wind, rainfall
• Animals bird, mice, rodents, canids, cats, etc.

24
Maggot Therapy Technically called Maggot
Debridement Therapy or MDT
Fly larvae are used to scavenge on dead tissue
associated with a wound. Fly larvae excrement,
termed allantoin has a high ammonia content
which appears to serve as an antibiotic.
25
Wounds on the Battlefield in World War II
It has been noted by war surgeons that wounds
incurred by troops in which fly larvae were
feeding had much less gangrene and healed more
quickly than wounds that were protected from
flies
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Phaenicia sericata the green blow fly. This
species feeds only on necrotic (decayed) tissue.
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Interesting and True

• Maggot therapy is much more commonly used in
  Great Britain and Europe than in the U.S.
• There have been about 25,000 treatments in Great
  Britain since 1995.
• Ronald Sherman, M.D. is the pioneer of maggot
  therapy in the U.S. He is located at U. of
  Calif., Irvine.

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Maggots Feeding at Edge of an Ulcerating Wound on
Foot
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Maggots Cleaning Up a Wound Associated with an
Amputation
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Vertebrate Biology/Taxidermy Skull and Skelton
Preparation
31
A Skull Cleaned by Dermestid Beetles
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Trays of Vertebrate Skulls in Dept. Of Vertebrate
Biology, Univ. of Michigan
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A Great Horned Owl Skeleton
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Dermestid Colony Housing
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Larval and Adult Dermestids Working on Jawbone
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Bears Skull Being Cleaned
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Dermestid Beetles Are Economic Pests and Will
Scavenge on Anything Organic of Both Plant and
Animal Origin

• Destroy woolen carpets, upholestry and rugs
• Consume insects on pins in museum and university
  collections
• Stored furs, leather and skins
• Meat, cheese and stored products
• Materials made of silk

38
Dermestids are Beneficial in Terms of

• Their use in vertebrate skull/skeleton
  collections
• Their forensic use as we have seen