1. T. Trimpe 2009 http://sciencespot.net/
Forensic Entomology
Insects as Evidence
Warning: Some material in this presentation and related videos may be too graphic for some people.
T. Trimpe

2. Cool Jobs: Forensic Entomology
What do they do?
Forensic entomologists apply their knowledge of entomology to provide information for criminal investigations.
A forensic entomologist’s job may include:
Identification of insects at various stages of their life cycle, such as eggs, larva, and adults.
Collection and preservation of insects as evidence.
Determining an estimate for the postmortem interval or PMI (the time between death and the discovery of the body) using factors such as insect evidence, weather conditions, location and condition of the body, etc.
Testifying in court to explain insect-related evidence found at a crime scene.
Did you know? Maggots can be used to test a corpse for the presence of poisons or drugs. Some drugs can speed up or slow down the insect’s development.
Cool Jobs: Forensic Entomology
Discovery Video

3. Insects as Evidence
Forensic entomologists use their knowledge of insects and their life cycles and behaviors to give them clues about a crime.
Most insects used in investigations are in two major orders:
1 – Flies (Diptera) and
2 – Beetles (Coleoptera)
Blow Fly
Carrion Beetle
Species succession may also provide clues for investigators. Some species may to feed on a fresh corpse, while another species may prefer to feed on one that has been dead for two weeks. Investigators will also find other insect species that prey on the insects feeding on the corpse.
Images: Top Right - Chart -

4. Click the image to view a video about the Body Farm!
Other Factors
Weather data is also an important tool in analyzing insect evidence from a corpse. Investigators will make note of the temperature of the air, ground surface, the interface area between the body and the ground, and the soil under the body as well as the temperature inside any maggot masses. They will also collect weather data related to daily temperature (highs/lows) and precipitation for a period of time before the body was discovered to the time the insect evidence was collected.
Other factors that might affect their PMI estimates:
Was the body enclosed in an area or wrapped in a material that would have prevented flies from finding the corpse and laying eggs?
Were other insect species present that may have affected the development of the collected species?
Were there drugs or other poisons in or on the body that might have affected the larvae’s development?
Did you know…
The “Body Farm” in Knoxville, Tennessee is a university research facility to investigate human decomposition under various conditions in order to understand the factors which affect its rate.
Click the image to view a video about the Body Farm!

5. Blow Fly Metamorphosis
Blow flies are attracted to dead bodies and often arrive within minutes of the death of an animal. They have a complete life cycle that consists of egg, larva, pupa, and adult stages.
1st – Adult flies lay eggs on the carcass especially at wound areas or around the openings in the body such as the nose, eyes, ears, anus, etc.
2nd – Eggs hatch into larva (maggots) in hours.
3rd– Larvae continue to grow and molt (shed their exoskeletons) as they pass through the various instar stages.
1st Instar - 5 mm long after 1.8 days
2nd Instar - 10 mm long after 2.5 days
3rd Instar – mm long after 4-5 days
4th – The larvae (17 mm) develop into pupa after burrowing in surrounding soil.
5th – Adult flies emerge from pupa cases after 6-8 days.
Adult
Pupa
Eggs
3rd Instar Larva
1st Instar Larva
2nd Instar Larva
It takes approximately days from egg to adult depending on the temperatures and humidity levels at the location of the body.
Image:
Information: and

6. Fly Comparison Blow Fly Drosophila melanogaster 5 days 1days 5.5 days

7. Examples of Diptera (Flies)
Early Stage Decomposition
Blow & Greenbottle Flies
(Calliphoridae)
Metallic thorax and abdomen
Flesh Fly
(Sarcophagidae) Striped thorax
Life Cycle of a Calliphoridae Fly
Late Stage Decomposition
House Fly
(Muscidae)
Cheese Skipper
(Piophilidae)
Informational Source: Images: Top Left - Middle-Left: Top Right - Bottom -

8. Examples of Coleoptera (Beetles)
Early Stage Decomposition
Early to Late Stage Decomposition
Rove Beetles
(Staphylinidae)
Predator of fly eggs
Clown Beetles
(Histeridae)
Predator of fly eggs
Carrion Beetles (Silphidae) Adults & larvae feed on fly larvae
Late Stage Decomposition
Ham & Checkered Beetles (Cleridae) Predator of flies & beetles;
also feed on dead tissue
Hide Beetles (Scarabidae) Usually the last to arrive
Skin Beetles (Dermestidae) Feed on dried skin & tissues
Informational Source:
Images: &

9. Let’s give it a try …
Click the image above or click here to visit the website at

10. FF: Worksheet http://youtu.be/CcVH5xaI-uw Forensic Files: Insect Clues
Forensic Science: Fundamentals & Investigations, Chapter 11

11. T. Trimpe 2009 http://sciencespot.net/
Crime Solving Insects
What happened to Porky?
Presentation developed for use with the Crime Solving Insects activity available at
Image:
T. Trimpe

12. Things to Remember …
The progression of insect life follows a pattern, and the developmental rates of flies are relatively predictable.
The rate of insect development is influenced by temperature because insects are ectothermic (“cold blooded”), which means their body temperatures are largely dictated by the outside temperature. Only when the outside temperature warms an insect’s internal body temperature to its critical level can the insect become active (and eat and grow).
The postmortem interval—the time between death and discovery of the corpse – can be estimated using insect evidence and temperature data along with other factors, such as the presence of drugs in a corpse and conditions related to the corpse itself (wrapped in a material, in a closed room, exposed to outside conditions, etc.)
Not all fly species are found everywhere, and this can provide important information also. For example, the skipper fly, Piophila nigriceps (pie-oh-FEEL-ah NYE-greh-cehps), is found only in urban settings. House flies, blow flies, and flesh flies can be found in both urban and rural settings.

13. Metamorphosis
Flies, beetles, and many other insects have complete metamorphosis, which consists of four stages – egg, larva, pupa, and adult.
After the adults mate, the females lay eggs onto corpses - usually near natural body openings or wounds.
Feeding activity is usually seen in the head region first (mouth, nostrils, eyes, ears), followed by the excretory and reproductive openings. The trunk of the body is invaded much later in the process.
The length of the life cycle varies between different fly species and is dependent on temperature.

14. Stages of Decay 1 - Fresh Stage
Begins at the moment of death and lasts until the body becomes bloated.
Blow flies and flesh flies are among the first to find the body.
Predatory wasps and beetles may arrive later to feed on the maggots (but not the corpse).
2 - Bloated Stage
Begins when the body becomes inflated due to the production of gases from bacteria that begin to putrefy the body or cause it to decompose.
House flies now join the other flies and their maggots form feeding masses that help to liquefy the tissues of the body.
3 - Decay Stage
Begins when the skin breaks and the gases escape.
Maggot masses are large and very active as they grow older and larger.
This is the stage of decomposition that smells bad.
At the end of this stage, the maggots leave the corpse in search of a place to pupate in the soil.
4 – Post-Decay Stage
Most of the flesh is gone from the corpse, with only cartilage, bone, and skin remaining.
This stage is devoid of flies. Some beetles continue to feed on the highly desiccated or dried remains.

15. Case Studies For each case:
1 – Review the police report and weather report.
2 – Examine & document the collected evidence.
Measure the length of the maggots & pupae. Record your data in the chart.
Consult the Species Key and the tables on your lab page to determine the various fly species that were found on the corpse and their ages.
3 – Use the information from the reports and your examination to answer the questions.
Mark the colors
Green
Red

16. Green
Red

17. Case #1: Oh, Deer!
Police Report: The body of a female deer was found behind a fence along a busy two-lane road on the edge of the city limits of Charlotte. Animal Control was called and reported no apparent wounds on the body. It was not hunting season.
Weather Report: Daytime temperatures have been fairly consistent for the past three weeks, ranging from 70 to 74º F.
Questions:
1. Approximately how long has this animal been dead?
2. Why are maggots of different ages found in the body?
3. Other than temperature, what abiotic (external to the corpse) conditions would you want to obtain from the weather station to help you to be more confident of your time of death estimation?
Species & Stage
Size
(mm)
Age

18. Case #2: Canine Caper
Police Report: The body of a large pit bull terrier was found inside a walk-in basement at a home in Cary. Maggots were found concentrated in the head and region behind the shoulder. The windows were closed, although the open curtains allowed sunlight to enter, and the air conditioner was set at 72º F.
Weather Report: Daytime temperatures have been variable over the past three weeks, ranging from 75 to 94º F. Skies have been sunny.
Questions:
1. Approximately how long has this animal been dead?
2. What effect, if any, do the outside temperatures have on your estimation of time of death in this case?
Species & Stage
Size
(mm)
Age
3. How does the fact that the windows were closed relate to the populations of flies you observed in and around the corpse?
4. Do you suspect foul play? Explain.

19. Case #3: Dandy’s Death
Police Report: The body of a young male horse was found in a pasture in a small town near Wilmington. The autopsy from the vet school reveals that the cardiac glycoside, oleandrin (a powerful heart stimulant), was present in the body. Oleandrin is found in the oleander plant. Oleander is a common ornamental shrub in this area, but none grows within 200 feet of the pasture.
Weather Report: Daytime temperatures have been unusually warm over the past three weeks, ranging from 84 to 86º F.
Species & Stage
Size
(mm)
Age
Questions:
1. Approximately how long has this animal been dead?
2. What effect, if any, does oleandrin have on your estimation of time of death?
3. What effect, if any, does temperature have on your estimation of time of death in this case?
4. Do you suspect foul play? Explain.

20. Case #4: Porky’s Peril
Police Report: The body of a large pot-bellied pig was found in a dense stand of evergreen trees far from any urban area in Buncombe County. Hairs around the pig’s neck were worn away in a band pattern.
Weather Report: Daytime temperatures have been average over the past three weeks, ranging from 70 to 73º F. Temperatures in the woods would be approximately 5 degrees cooler due to the lack of sun in the shady environment.
Questions:
1. Approximately how long has this animal been dead?
2. What effect, if any, does temperature have on your estimation of time of death in this case?
3. Do you suspect foul play? Explain.
Species & Stage
Size
(mm)
Age