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

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Morphology (Body Shape)

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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

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Morphology (Body Shape) (continued)

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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

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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

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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)