1. FORENSIC ENTOMOLOGY
PTHS
RESCIGNO

2. What is Forensic Entomology?

3. Entomology Inquiry – ON CLASSROOM
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1. Define entomology
2. Explain “Time Since Colonization”
3. Multiple techniques used to assist in the work of forensic entomolgy
4. Summarize Eclosion and how it is valuable to an investigation
5. Three different insect species that infest and feed on a body
Include image and description
Important information each species provides to an entomologist

4. Forensic Entomology
The study of insects and their relationship to time of death.
commonly called upon to determine the postmortem interval or "time since death" in homicide investigations.

5. Entomology based on the age of the insect present
"Time Since Colonization"
number of different techniques
species succession
larval weight
larval length
accumulated degree hour technique

6. Life Cycle Stages of a Blow Fly
1. Egg
2 – 4. Larva
5. Pupa
6. Adult

7. Life Cycle 1St Stage  Eggs
2Nd Stage  First Stage Larva hatch from eggs
Maggots feed on dead tissue.
3rd Stage  Second Stage Larva Molts from first stage larva
4th Stage  Third Stage Larva Molts from second stage larva
Masses of third stage maggots produce enough thermal energy to increase ambient temperature up to 10 deg C

8. Life Cycle 5th Stage  Third stage Larva molts into Pupa
6th Stage  Pupa develops into adult fly
Approximately 2 weeks from egg to adult
Depends on species and environmental conditions
Temperature/Exposure/Humidity

9. Life Cycle of the Blow Fly
Blow Flies are most commonly the first insects to infest a dead body.
Lay eggs around natural body orifices
Nose
Eyes
Ears
Anus
Penis
Vagina
Open Wounds (Gun shot, Stab, Puncture wounds)

10. Accumulated Degree Hours
Technique used to determine Eclosion
period of time it takes an insect to hatch from a fresh egg.
Eclosion times have been tabulated to complete this development in various insect species.
In a blow fly, this time has been determined to be 21.2 hours at 20 degrees C
ADH = Temperature in C x Eclosion of species

11. Accumulated Degree Hour
Based on a mean temperature of 20 degrees C
For a blow fly
ADH = 20 deg C x 21.2 hours
Average ADH = 424 degree hours for a blow fly to emerge from its egg
For a specific environmental temperature 
ADH is divided by the temperature

12. Calculating Eclosion using ADH
For a specific environmental temperature
Average ADH is divided by the temperature
At 25 degrees C  424 hours / 25 = 17 hours
Eclosion of a blow fly at 25 C = 17 hours

13. ADH Review
Eclosion for a black blow fly has been determined to be 23 hours. An average ADH for this insect is 424 degree – hours.
What was the environmental temperature of the crime scene where these insects were collected?
Would you expect the temperature to higher or lower than 20 degrees C? WHY?

14. ADH Review 424 deg – hours _____________ = Eclosion time Enviro Temp
Solve for Enviro Temp.
424 deg-hours
Enviro Temp = ____________ = 18.4 deg C
23 hours

15. Question of the Day
Because insects are cold blooded organisms, it can be concluded that
A. insects will develop faster when found on bodies in cooler areas.
B. warmer air temperature will mean the body will decompose at a slower rate.
C. heavy rain will cause insects to develop faster
D. Bodies exposed to large amounts of sunlight will see increased growth rates in insects.

16. ADH Extension: How it is used in a criminal investigation.
Example 1
A type of insect has a threshold temperature of 58 degrees F
On a day with a high temperature of 68 F and a low of 54 F, calculate the ADH available to its eggs received on the first day.

17. ADH Extension What is known from the problem?
High Temp = 68 F Low Temp = 54 F
Threshold Temp = 58 F
What is the significance of this temp?

18. Solving the problem to find ADH
1. Find the average daily temperature
Avg Temp = (68+54 F) / 2 = 61 F
2. Subtract the Threshold Temp from the Avg Temp
61 F – 58 F = 3 F
This means that an average of 3 degrees of heat was available to the insect eggs.
3. Find the ADH
ADH = Temperature x Time
3 F x hours
ADH = 72 degree hours on the first day

19. Calculate the total Accumulated Degree Hours for the first two days
High Temp = 76 F Low Temp = 52 F
Follow the steps!

20. Solution: Total ADH for 2 days
ADH for day 1 = 72 degree hours
ADH for day 2 = 144 degree hours
Avg Temp 64 F – Threshold of 58 F = 6 F
ADH day 2 = 6 F x 24 hours = 144 degree hours
Total ADH = 72 deghours deghours =
216 degree hours
How is this data used?

21. ADH Sample Problem 2
A body linked to a missing persons case has been discovered. Police are now investigating two possible suspects for murder.
You have been called in as the Forensic Entomologist to examine the body and assist the medical examiner.

22. The body was found fully clothed on the first floor of a single family home.
You find maggots in the second instar stage on the body.
The temperature within the home was a constant 72 degrees F.

23. The insect’s threshold temperature is 64 degrees F
Data you have on this species of fly is as follows
Minimum of 320 ADH to reach the second instar
Minimum of 480 ADH to reach the third instar
How long has the body been in the home?

24. Solution ADH = Temp x Time Solve for Time  Time = ADH / Temp
72 F – 64 F = 8 F
Time = 320 deg-hours / 8 F = 40 hours
Time = 480 deg-hours / 8 F = 60 hours
Body has been in home 40 to 60 hours
How is this information used?

25. Decomposition of a Body
Insects will immediately colonize a body.
Bacteria, Fungi, and animals
Depends upon where the body is located
Environmental conditions
Some insects thrive in the sun vs. shady conditions
Also dependent upon stage of decomposition
Beetles will consume bone and cartilage
Leakage of body fluids will lead to the disappearance of some insects and the appearance of others.

26. The Missing Children Forensic Entomology at Work Part 1
Part 2

27. The Body Farm - Decomposition
Nat Geo
Decomposition of a Pig

28. Stages of Decomposition 3.

29. Stages of Decomposition
1. Fresh Stage – blow flies
Ants
2. Bloated Stage – putrefaction begins
Rove beetles and Carrion beetles
3. Active Decay Stage
Maggots feed around natural orifices of body
4. Advanced Decay Stage
Beetles
5. Dry Stage
Centipedes, millipedes, cockroaches

30. Investigation and Collection of Insects from a Body
1.Inspect foliage and test soil to see if body has been moved.
2. Collect specimens from different areas of the body, clothing, surrounding environment (indoor/outdoor)
3. Collect 100 maggots
4. Collect pupae from body, clothing, hair, soil
5. Collect empty pupae cases from body, clothing, and surroundings

31. Investigation and Collection of Insects from a Body
6. Collect adult flies
7. Collect beetles
8. Collect any other insects at scene
9. Collect leaf litter near remains of body if outdoors (enough to fill a coffee can).
10. Place all insects in vials with food

32. Labeling and Exclusions
Keep insects collected from different parts of the body separate from one another.
Insects would not be present if the body is wrapped in plastic, buried deep underground, and in frozen or freezing temperature/conditions

33. What are the top causes of automobile accidents?
What have you learned about this in Driver’s Ed?

34. Accident and Criminal Investigations
Insects theorized to be within the top 20 causes of automobile accidents
What evidence would support this statement?
Consider an automobile accident.
Examination of the fragmented remains of insects that have impacted and lodged onto the front fascia, windshield, and radiator of automobiles.
Yields evidence to the probable path of an automobile through particular areas
Pinpointing the location and areas of travel are of unique importance in some investigations

35. General Applications Detection of abuse in children
Neglect in the elderly
Automobile/Aircraft accident studies
Interpretation of blood spatter patterns
Determination of time of death
Recovery of human blood from digestive tract
Toxicological analysis

36. NATIONAL GEOGRAPHICS THE BODY FARM