Transcript Entomology

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Entomology

Review: Forensic entomologists study
INSECTS
(true wings)
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Based on the life cycle stage of
insects, entomologists can determine
how long a body has been dead;
determines PMI (postmortem interval)
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What is Forensic Entomology?

Review: Definition
 The
application of the study of arthropods
to criminal or legal cases
- includes spiders, centipedes, blow flies,
millipedes, crustaceans
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Insects 101
Vital role in “recycling” carcasses
 Only animals to have “true wings”
 First to colonize a corpse; do so in a
predictable pattern
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Necrophagous insects: insects who eat dead
flesh
- through the study of taphonomy, scientists
can tell how processes such as wind, rain,
and insects affect a corpse
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Insects 101 continued…

6 legs, 3 body
segments (head,
thorax, abdomen)
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Nearly 1 million
species
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Have an
exoskeleton
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Insect Life Cycle
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Collecting Insects at a Crime
Scene
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Only certain insects invade dead bodies
- Vary based on environment, time, weather
 Necrophilious insects can sense chemical
changes in decomposing tissue and register
it as “food”
 Attracted to dark, moist areas on body
(wounds, nose, mouth, eyes, anal openings)
 Insects are captured with nets or forceps
and put into ethyl alcohol for preservation;
labeled; soil samples also taken
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Postmortem Interval
PMI (Postmortem Interval) is the time
range for when a crime occurred and
how long ago the victim was killed
 A minimum and maximum time since
death are established
 Extremely hard to establish an
accurate maximum PMI because as
time/decomposition continues, the
more unclear time of death becomes
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PMI continued…
Categorizing insects and classifying
them is called the science of
taxonomy
 Insects are named based on their
Genus species name
Ex. Calliphora vicina (blue bottle
fly)
 PMI is based on ecological and faunal
study of cadaver (stages of
development of insects on body)
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Infestation order
1.
2.
3.
4.
Necrophagous species: flies that feed off of
body
Predatory and Parasitic species: beetles,
ants, bees, wasps that feed off of the
necrophagous species
Omnivorous species: beetles, wasps, and
ants that feed on both human body and
other insects
Incidental (Normal) species: spiders and
other naturally occurring insects found in
the environment
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Stages of Decomposition
1.
Fresh Stage - at moment of death;
body temp falls to surrounding
temps; blowflies land on body and lay
eggs; maggots hatch;
predators/parasites also arrive
2.
Bloated Stage - bacteria in the body
release gas; body is bloated and
swollen; temp is very hot; maggot
masses bigger; body fluids seep out
of body
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Stages of Decomposition
3.
Decay Stage - skin of corpse begins
to crack; gases escape; lose bloated
appearance; strong foul odor; more
beetles arrive
4. Post-Decay Stage - not much of
body left except bones, cartilage,
skin, and hair; new kinds of beetles;
mites infest soil below body
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Stages of Decomposition
5. Skeletal Stage - only bones and hair
are left; no more insects left on
skeleton
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Other Information on Insects
Insects can provide DNA of the victim
by removing the waste inside the
insect
 Insects can also provide drug/chemical
evidence because they are feasting on
the tissues of the body
 Insects can also indicate location,
travel, and geography of a victim
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