1. Forensic Entomology
STEM

2. What is a Forensic Entomologist?
A scientists who uses insects to help solve crime.

3. How do insects help solve crimes?
A dead body attracts insects
Insects lay eggs on the body.
Hatching larva use body as food.
Larva grow at a predictable rate.
The Post-Mortem Interval (PMI-how long the body has been dead) can be determined by measuring and identifying the developing larva.

4. Forensic Entomology - The Crime Scene Video

15. Insect Succession Can be used to determine PMI
Different species of insects prefer different stages of decomposition
“I prefer my corpse dried”
“The fresher the better!”
“Juicy and smelly suits me just fine!”

16. Stages of Decomposition
Living
Initial decay
Putrefaction
Black putrefaction
Butyric fermentation
Dry decay

17. Initial Decay--Day 1-3
Bacteria, present in the intestine to digest food, begin to eat away at the intestine itself.
Intestine decays releasing bacteria and digestive enzymes into body cavity.
Blow flies and house flies immediately begin to lay eggs on the defenseless body.

19. Putrefaction--Day 4-8
Bacteria continue to break down body producing large amounts of gasses
Gasses inflate the body like a balloon.
Larval flies move throughout the body, eating the partially digested flesh.
Smell attracts other species flies and beetles.
Rate of decay increases.

21. Black Putrefaction 10-20 days after death
Bloated body collapses and flattens.
Large amounts of fluids are released.
Flesh is creamy and black where exposed.
Several generations of flies are present.
Wasps parasitize maggots.

23. Butyric Fermentation 20-50 days after death
Remaining flesh is decomposed and corpse begins to dry out.
Cheesy smell attracts new organisms.
Body ferments and is covered with mold.
Hardening of body makes it difficult for maggots to feed.
Chewing beetles and their larva move in.

24. Dry Decay 50-365 days after death
Body is dry and decays slowly.
Hair and bones are all that remain.
Hair is fed on my moths and bacteria.
Mites may be present and feed on bacteria.

26. Insect Succession Body Condition Species Present Fresh Bloated
Blow Fly Screw Worm Fly Flesh Fly
House Fly Hairy Maggot Fly Bottle Fly
Bloated
Blow Fly Flesh Fly
Hairy Maggot Fly House Fly
Bottle Fly Roves Beetle Humpback Fly
Cheese Fly Screw Worm Fly Scavenger Fly
Active Decay
Blow Fly Flesh Fly House Fly
Rove’s Beetle Cheese Fly Carrion Beetles
Advanced Decay
Roves Beetle Cheese Fly
Checkered Beetles
Dried Remains
Picnic Beetle Dermestid Beetle

27. Factors that affect decay rate and growth rate of flies
Temperature--the warmer the climate, the faster the decay.
Season--early spring will decay slower, because the insect population is still relatively low.
Degree of corpse enclosure--the more exposed, the faster the decay.

28. Classification of a House Fly
Kingdom - Animal
Phylum - Arthropods
Class - Insects
Order - Diptera (All Flies)
Family - Muscidae
Genus - Musca
Species - domestica
Musca domestica

29. Life Cycle of a Fly Flies lay 100-150 eggs at a time.
Eggs hatch-1st instar
Larva molt-2nd instar
Larva molt again-3rd instar
Pupa -- cocoon
Adult fly

31. Another Look

33. Egg Stage Most flies lay 100-150 eggs at a time.
The eggs are small and oblong.
They are white or cream colored.
It takes 8-14 hours for the eggs to hatch after they have been laid.
Flies only lay eggs in daylight.

34. Another look at eggs

35. Larva Molt (shed their skin) twice after hatching
Breath through anterior and posterior slits called spiracles

36. Instar Maturation of Larva
1st instar larva take 8-14 more hours until they are ready to molt.
2nd instar larva take 2-3 days to molt.
3rd instar larva take 7-8 days until pupal maturation.
Pre-pupal 3rd instar larva.

37. Spiracles are distinct
Different species of fly larva have different spiracle characteristics
Peritreme
Spiracular Slits

38. Identifying Maggots by Spiracular Slits
Maggots can be identified by their distinguishing spiracular slits.

39. Pupa
Once larva mature they stop eating and metamorphose into an adult fly.

40. Basic Anatomy of an Adult Fly
Insects have three body parts
Head
Thorax
Abdomen
Six Legs
Wings