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

3. Entomology is the Study of Insects
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4. 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

5. 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 -

6. Forensic Entomology is Applied Biology
If it weren’t for decomposition of all living things, our world would fill up with dead bodies.
When an animal dies, female insects will be attracted to the body. They enter exposed orifices or wounds and lay eggs or larvae.
A forensic entomologist:
identifies the immature insects
determines the size and development of the insects
calculates the growth of the insects and passage through stages of the life cycle in laboratory
compares the growth against weather conditions to estimate time of oviposition

7. Click the image to view a video about the Body Farm!
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!

8. Differentiate between PMI and Time of Death
These may not always equate.
Post mortem interval is restricted to the time that the corpse or body has been exposed to an environment which would allow insect activity to begin.
Closed windows
Body in box or bag
Cold temperatures
Deeper burial

9. Insect species arrive at a corpse in waves like clockwork
Calculate the heat/thermal energy (accumulated degree hour) required for each stage of the Green Bottle Fly’s life cycle.
Possibly the greatest potential source of error in using arthropod successional patterns lies in the collection of speciments.
Must only be done correctly to accurately sample the insects.

10. 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

11. Image: http://www.nlm.nih.gov/visibleproofs

12. 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 -

13. 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: &

14. Five Stages of Decomposition Fueled by Insect Activity.
Fresh
Bloat
Decay
Post-decay
Dry (skeletal)

15. Fresh Begins at death Flies begin to arrive
Temperature falls to that of the ambient temperature.
Autolysis, the degradation of complex protein and carbohydrate molecules, occurs.
Gasses produced by the metabolic activities of the anaerobic bacteria first cause a slight inflation of the abdomen. The carcass may later assume a fully inflated, balloon-like appearance. Adult and larval blowflies in large numbers attracted to fluids seeping from body, normal soil dwelling fauna depart soil because of seepage of fluids; some muscid flies and ants which can feed on larvae and retard maggot activity. 15

16. Bloat Swells due to gases produced by bacteria
Temperature rise of the corpse
Flies still present

17. Decay Gases subside, decomposition fluids seep from body.
Bacteria and maggots break through the skin.
Large maggot masses and extreme amounts of fluid.
Unpleasant odor
Larvae beginning to pupate.
Corpse reduced to about 20% of it’s original mass.
Decay Stage - Black Putrefaction (Days 5-11) -- Decay stage begins when the abdominal wall is broken, allowing gasses to escape and carcass deflates. This process is facilitated by feeding activities of larval flies present on the exposed remains. Adult flies start to leave body, mainly larval mass. Carcass begins to assume a blackened, wet appearance, and most of the flesh will be removed by the maggots. Toward end of this period, carcass will begin to dry and beetles feed on drier tissue. Flies start to pupate. Predatory beetles such as rove beetles and histerids come to feed on other insects. 17

18. Post-Decay Carcass reduced to hair, skin, and bones.
Fly population reduced and replaced by other arthropods.
Hide beetles are dominant in dry environments.
Mite and predatory beetle populations increase.
Postdecay Stage - Butyric fermentation (Days 10-25) -- In dry habitats, remains consisted of dry skin, cartilage and bones. Site for dermestid beetles, histerids, fly pupae, immature and adult rove beetles. In wet habitats, a large quantity of wet, viscous material, termed byproducts of decomposition, was found in the soil under the remains. Site for immature and adult moth flies, sphaerocerid and muscid flies, rove beetles. 18

19. Dry (Skeletal)
Does not always occur especially if corpse is in a wet region. Maggots will stay longer and hide beetles will not appear.
In wet environments the hide beetles are replaced with nabid and reduviid insects.
The corpse is reduced to at least ten percent of the original mass.
In the last stage (Skeletal Stage), only bone and hair remain.
Dry Stage (Days 25 +) -- This stage is reached when mainly bones and hair remain. Odor is primarily that of normal soil and litter. Some dermestid beetles, histerids, fly pupae, immature and adult rove beetles, normal soil fauna (mites) start to return. Can last several months to even years. 19

21. The End

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