Entomology and Taphonomy Flashcards
(27 cards)
What is forensic entomology?
the study of insects as it relates to criminal investigations, commonly used to estimate the PMI
In addition to the PMI, what else can insect activity indicate?
abuse/peri-mortem wounds and drug abuse
What is taphonomy?
the study of changes after death, often encompasses environmental factors
What is characteristic of an ante-mortem fracture?
Moist and greasy, moisture will be lost over time after death
What is characteristic of a post-mortem fracture?
Clean, brittle (bone is dry), often parallel to the cross section of the long-axis of the bone
What are the 4 stages of decay?
- Death
- Fresh
- Bloat (more detail in another question)
- Active Decay (more detail in another question)
- Also the dry stage - bones
How does the bloat stage of decay occur?
- bloating of abdominal cavity due to active proliferation of bacteria
- Increased odor
- marbling of skin, green-purple U shape
- skin slippage on extremities (glove look)
- perforation of abdominal cavity due to insect activity, gasses released
How does the active decay stage occur?
- enhanced insect activity
- deflation of body cavity due to perforation
- wet appearance
- very strong odor
- total loss of 50% body mass
how are insects used to find buried remains?
- survey soil for insect activity
- blow fly can lay eggs in loose soil and larvae migrate to body
what are some field techniques to ID a grave?
- roughly rectangular disturbance, visible months later
- pile of soil and disturbed vegetation
- grave surface forms a mound (mixed with air and body)
- grave eventually becomes a depression with rain and time
- plant succession
- soil takes years to become uniform with the surroundings
What other cases utilize entomology?
- livestock food contamination
- Abuse and neglect (bugs in diapers, beg sore bugs)
- can have toxins or chemicals in stomachs (indicate drug use)
- tell if a corpse was moved
What was the first documented use of entomology?
Sun Tzu’s Washing Away of Wrongs 13th century. Details a murder that was solved by flies colonizing a sickle
When, and who, disproved the theory of spontaneous generation?
1626 Francesco Redi, using covered and uncovered jars with raw meat
How did Matthieu Orfilia contribute to entomology?
Mid-1800s, pathologist, systematized 30 types of insects and anthropods that feed on and oviposit in humans
How was entomology used in the Steven Truscott case?
- Original PMI was wrong
- proven that the species of fly does not lay eggs at night, thus, Truscott had an alibi for the night
What is the insect succession pattern in the first stage of decay: fresh?
- necrophagous species
1. Caliphordae (blow and green/blue bottle fly)
2. Sarcophagidae fly
3. Silphidin beetle (carrion-eating)
What is the insect succession pattern in the second stage of decay: bloat?
- predatory species (eat other insects)
1. histeridae beetles
2. Staphylinidae
What is the insect succession pattern in the third stage of decay: active decay?
- Hymenoptera
- Parasitic Wasps
What is the insect succession pattern in the fourth stage of decay: dry?
- species that make use of dry remains
- spiders, springtails, some mites, round worms
What is the main challenge when estimating PMI?
Temperature as it effects growth rate - must record temp at scene
What is the life cycle of a blowfly like?
- Day 1: eggs
- Day 2: larvae emerge (instar)
- Day 3-7: larvae grow (pre-pupae)
- Day 8-9: pre-pupation form hard cocoon shell, develop adult features
- Two weeks: full adult emerges
- Warmer temps could expedite this
How are maggots aged?
- Based on spiracles (breathing parts)
- 1st Instar have 1, 2nd have 2, 3rd have 3
How is blowfly colonization used to estimate PMI?
- estimation of age is better than succession
- temperature dependent growth (below 15 degrees they go dormant)
- different species develop at different rates
- useful 1-30 days post-mortem
What are the 4 main problems with using entomology to estimate PMI?
- Maggot mass: generate heat, increase growth rate
- geography: species grow differently in different locations
- Buried/clothed remains: may limit ability to colonize immediately
- Larval crowding: competition for resources, affects growth rate
