Entomology

1. Entomology Chapter 10

2. Insects!- Forensic Entomology • Observes and records data about the environmental conditions, including temperature, moisture, and wind, around the body • Entomologist collect insect evidence from on, above, below the victims body as well as surrounding area • Within minutes, insects arrive to lay their eggs on the warm body- attracted by the smell of the first stages of decomposition • Eggs will hatch and feed on decomposing tissues

3. Common insects • Blow flies are common example • Attracted to 2 gases : putrescine and cadaverene • As corpse continues decomposition, other insects arrive • Wasps lay eggs on maggots already on the body • Wasp larvae live as parasite inside the maggots • Cheese skippers arrive when putrefaction is under way; Attracted to body fluid seepage • Mites and beetles finally arrive in drier conditions- feed on dry tissue and hair

4. Did you know? • To establish how different environmental conditions affect the appearance and rate of development of insects, University of Tennessee professor William Bass established the Body Farm in 1980. This has helped forensic experts interpret the evidence about the time of death much more accurately. • Body farm- research facility where human decomposition can be studied in a variety of settings… used to gain understanding of human decomposition, with the use of various techniques to find out timing and circumstances of death

5. Blowflies • First insects to arrive • Very useful in determining time of death • Exhibit different stages as they develop from egg (larva stages or instars), pupa, to adult • If scientists know how long it takes for the various stages of development at given temperatures…can determine when blow flies arrive at the body…generally time the body died • Observe size, color, mobility, presence/absence of crop, spiracle slits

6. 3 Stages of Larva • Has one V shaped slit (1.8 days old) • Has two slits (2.5 days) • 3 slits (4-5 days) Ex: if corpse has blowfly eggs, then approximate time of death = 24 hours or less Ex: if corpse has 3rd stage larvae, time of death = 4-5 days Ex: if corpse has pupae, time of death = 18-24 days

7. Factors • Temperature, moisture, wind, time of day, season, exposure to the elements, and variations among individual insects • Insects CANNOT provide an exact time, only estimate • Accumulated Degree Hours (ADH): process when insects collected at the crime scene and then raised in the lab under the same environmental conditions as found at the crime scene.

8. Steps for Accumulated Degree Hours (ADH) • Immediately preserve the insects from the crime scene so you know how old they are the time of discovery of the body • At the crime lab, raise some of the insects from the crime scene in the same conditions as those found at the crime scene • Record the length of time for development under the specific conditions found at the crime scene • Compare the insects raised at the crime lab to those found at the crime scene

9. Isomegalen Diagrams • Used to determine the age of a larvae based on estimated growth of larva • Helped to determine PMI

10. Isomegalen Diagram