1. Forensic Entomology
“ We fat all creatures else to fat us, and we fat ourselves for maggots. Your fat king and your lean beggar is but variable service- two dishes, but to one table. That’s the end.”
-HAMLET (ACT 4 SCENE 3)

2. Forensic Entomology
Application of the study of insects to legal issues
Determination of time (PMI) or site of human death
Cases involving possible sudden death
Traffic accidents with no immediately obvious cause
Possible criminal misuse of insects
Subfields:
1. Urban (ex. Termites)
2. Stored Product (food, beverages, kitchen)
3. Medicolegal (focus of this lecture)

3. China 200 BC- Sung Tzu Farmer in neighborhood killed
Death investigator- all bring their sickles (70-80)
Flies gathered at one sickle

4. Forensic Entomology Time of death estimates
Abuse cases: Open wounds in elderly
“Spatter” or insects walking ??
Check for drugs, poisons in insects
Beer, soda industry
Insects hidden in shipments
Crops affected
Pesticides and biological controls

5. Flies = Diptera Life cycle of flies: Egg
Larvae : 1st, 2nd, 3rd instars (stages)
Pupa
Adult

7. Egg Laying in Moist Area
Females cannot pierce skin. Lay eggs in mucous membranes of nose, mouth, eyes, open wound, scratches.
1st instar larvae: must nurse on liquid protein before their mouth hooks grow large enough to tear through flesh.
Clothing that sops up blood and other fluids.. becomes a nursery for the eggs

8. Egg Laying
Female has chemoreceptors on soles of her 6 feet and the ovipositor on the tip of the abdomen.
Can lay up to 400 eggs in 6 minutes

9. Flies must find carcass early, before it turns to mush
Flies can detect smell of decomposition -- as little as a few parts per million
special hair on flies that have chemical receptors (sensilla trichoidea)

10. Flies First flies lay down pheromones.. cause an oviposition frenzy
Eggs hatch hrs later
Larvae tear at exposed flesh with a pair of tiny mouth hooks

11. Maggots (larvae) Breath through anal spiracles
Metabolic heat send mass to surface to cool periodically
As maggots grow, put own layer of fat that eventually hides all internal organs except for the crop (feeding tube) – seen as dark red line extending back from mouth

12. Maggots grow- flattened rump, pointed mouth, ridges around the body
Use collagen splitting enzymes to break through connective tissue
Larvae bury heads in flesh
Some insects will remove most maggots and delay decomposition

13. Anal spiracles first instar: 1 anal spiracle
second instar: spiracles
third instar: 3 spiracles
Need third instar to distinguish species

15. Stop feeding after 3rd instar (1/2 inch long)
Maggots then drop to ground, seek darkness, moving light sensitive heads right and left as they move.

16. Need third instar to distinguish species
Internal mouthparts
“Teeth”- simple hooks or compound barbs?
Short and claw like or long like a saber?
If maggots not well preserved: rely on simple length of maggots: compare to day to day growth rates.

17. Pupa Bury in soil, move under leaves, carpets
Contract into short, thick plugs and wait for larval skin to harden
Metamorphosis into adults
New fly emerges from 1 week to 6 months later

18. Emergence of Adult Flies
Emergence—fleshy sac pops out of slit above the eyes
Sac fills with fluid, presses against top of pupal case, pops it open along a fracture line
Fly within thirty minutes

19. Typical infestation: a) Blow flies (bottles) -- few minutes
b) Flesh flies- within a day or two
c) Rove beetles, soldier flies – feed on developing maggots

20. Typical infestation
d) Cheese skippers, scuttle flies- feed on fermented protein of the later stages of decomposition
e) Mites- like dry cadaver
f) Clothes moths and spider beetles—completely desiccated remains

21. Example of post-mortem interval (PMI)
8-14 hrs for eggs to hatch
8-14 hrs to finish 1st instar
2-3 days 2nd instar
7-8 days- third instar

22. PMI 8-14 hours 48-72 hrs 168-192 hrs 232 – 292 hrs 9.6-12.2 days
(total time needed to reach 3rd instar)
days

23. PMI estimate affected by:
Temperature
Time of day
Time of year
Exposure?

24. Cooler weather- choose later range of 12 days; insects develop slower
Warmer weather – pick early part of range, 9 days; insects will develop faster

25. Typical Flies
Green bottle Phaenicia sericata: urban settings, open, sunlit
Black blow fly : Phormia regina rural areas
Green bottle: Phaenicia eximia : southern states
Holarctic blow fly: Protophormia terraenovae : north

26. Blow flies 1st to arrive Family Calliphoridae
Lays eggs (oviposits) within minutes and up to two days after death
Egg 3 instars  prepupae  pupae 
 adult
Calculate the age of the insects using the life stages
PMI= postmortem interval

27. Insects are also used to show movement of:
Victim
Suspect
Cars
goods

28. Case study #1 One puparium in barrel of gun
Many of the same puparia under floor mat of burned out car
Gun and car found 50 ft apart
Boyfriend claimed – crime of passion- only 2nd degree murder- left car after it wrecked

29. Prosecution- said he came back to burn car
Entomologist: gun was inside the car when larvae finished feeding and crawled away to find dark place to metamorphose into an adult.
50 ft too far for maggot to crawl

30. Case Study # 2 1980’s female body found, maggots collected
Some preserved, some raised to adulthood
Found sheep blow flies and shiny bluebottles which lay eggs the first day of death
Found one very large maggot ¾ inch
Would have meant the woman died three weeks earlier but she had been seen alive 2 weeks before

31. No other carcass nearby that may have been the source of the maggot
Mystery solved--- woman was a cocaine user

32. Taking field samples ½ in alcohol – 70-80% solution of ethyl alcohol
½ kept alive- raise to adulthood in the lab

33. Jobs at the scene Observations and notes at the scene
Climatological data
Specimens from the body
Specimens from near the body
Specimens under and near the body after the body is removed

34. Climatological data Ambient temp Ground temp Body surface temp
Under body temp
Maggot mass temp
Soil temp after body removed

35. Climatological data Weather data from station Max temp Min temp
Amt precipitation
Go back in time to when the victim was last seen

36. Observations Rural, urban, aquatic ?
Estimate # and kind of flying and crawling insects
Major infestations of the body
Eggs, larvae, pupae, pupal cases, cast larval skins, feces, feeding marks
Insect predation by beetles, ants, wasps, or insect parasites

37. Observations Compass direction Sunlight vs. shade Position of body
Photos

38. Weather station readings
Find your local weather station and collect information
Adjust data to compensate for:
Sun vs. shade
Windy hill or protected cove?
Maggot mass? (can be much warmer than air)
Ambient and ground temp at corpse may vary from weather station