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Forensic Entomology
Application of insects to legal issues
o Insects have 3 body segments:• Head• Thorax• Abdomen
Blowflies□ First arrivals; important in
establishing Post-Mortem Interval (PMI) or time since death
□ Attracted to natural body openings or open wounds
□ Bodies emit putrescene and cadaverine that blowflies can detect from a mile away.
Blowflies can be blue, green, or bronze
ADULT FLY LAYING EGG
1ST STAGE LARVA
2ND STAGE LARVA
3RD STAGE LARVA PUPA
BLOW FLY LIFE CYLCLE
Forensic Science: Fundamentals & Investigations, 2e Chapter 11
All rights Reserved Cengage/NGL/South-Western © 2016
Morphology (Body Shape)
5
o Blowfly larvae use hooks to dig and scrape at decomposing flesh to move the flesh toward the mouth.
Forensic Science: Fundamentals & Investigations, 2e Chapter 11
All rights Reserved Cengage/NGL/South-Western © 2016
Morphology (Body Shape) (continued)
6
o Spiracle configuration alerts investigators to the developmental stage of the instar. Larvae breathe through their spiracle.
Other Flies
Flesh fly- arrive within minutes of death. Lay live larva, not eggs
Housefly- can indicate abuse because of their attraction to feces and urine.
Coffin fly- smaller than fruit flies. If the body is wrapped, they may be the only insects that can infest the body.
Insect succession
Flies- blowfies, houseflies, flesh flies, coffin flies.
Ants and Wasps (predators of flies)Beetles- Clown beetle, surinam carrion
beetle, american carrion beetle, sexton beetle, hairy rove beetle, hide beetle
5 Stages of Human Decomposition
1. Fresh stage2. Bloated stage3. Decay4. Post-Decay5. Skeletal
1. Fresh stage□ Blowflies begin to
arrive; followed by their predators (ants, wasps)
2. Bloated stage□ Body inflated;
gases release□ Beetles begin to
arrive
3. Decay stage□ Skin broken by
maggots and bacteria
□ Only 20% of original mass remains
□ Odors from this stage often lead to discovery of bodies
4. Post-Decay stage□ Only 10% of
weight remains□ Change in insects
that are around; now there are clothes moths and hide beetles
5. Skeletal stage□ Insects are usually
gone but leave behind molted larval or pupal cases
Forensic Science: Fundamentals & Investigations, 2e Chapter 11
All rights Reserved Cengage/NGL/South-Western © 2016
Estimating Postmortem Interval
15
o Factors Affecting Development• Temperatures and environmental conditions • Lower limit threshold, If the temp is below 10o C,,
growth and development stopso Degree Hours
• Accumulated degree hours (ADH) is the number of hours at an adjusted average Celsius temperature than it takes an insect species to reach a particular stage of development.
Forensic Science: Fundamentals & Investigations, 2e Chapter 11
All rights Reserved Cengage/NGL/South-Western © 2016
Processing a Crime Scene for Insect Evidence
16
1. Death-Scene observations2. Collection of Meteorological Data3. Two Collections: Collect live
insects, and collect and preserve other insects from the body at the crime scene.
4. After Body Removal: Collect insects from the surrounding soil.
How is this useful to forensics?□ Determining time of death by
identifying species present and/or where they are in their life cycle to establish post mortem interval (time since death)