Forensic Science Unit 4 Forensic Biology: Day One Entomology
Get out your Time of death packet • If you turned it in last class period it should be in your folder
Forensic File #3 Part 1: A body has been found in a field with an internal temperature of 83oF. Using 1.4oF lost every hour, what is the PMI (post mortem interval)? In other words, how long have they been dead? Part 2: What if the internal temperature of the body was 73oF? How long have they been dead?
Your assignments • Insect Webquest • Body Bugs article questions • Paper on TABLE 4
What is Forensic Entomology? • Entomology is the study of insects. • Insects arrive at a decomposing body in a particular order and then complete their life cycle based on the surrounding temperature. • By collecting and studying the types of insects found on a body, a forensic entomologist can predict the time of death
Incomplete Metamorphosis 3 stages: Egg Nymph: has appearance of small adult; increases size with each molt Adult Complete metamorphosis 4 stages: Egg Larvae: wormlike stage (caterpillar) Pupa: inactive stage (chrysallis) adult What are the different life cycles of insects?
Complete metamorphosis • Holometabolous • The pig ear in the diagram shows a layer of what looks like a white crust. These are the fly eggs
Larva • Larva hatch and grow in steps called instars • Eventually the larva migrate from the corpse and develop into the pupal stage • During this time, the adult insect develops internally Two larval instars
Four Main Types of Carrion Species • Necrophagous--feed directly on the corpse • Flies (Diptera) • Beetles (Coleoptera) • Predators • Burying or Carrion beetles (family Silphidae) • Rove beetles (family Staphylinidae) • Hister beetles (family Histeridae)
Four Types continued • Species that feed on both the body and other arthropods • Ants • Wasps • Some beetles • Arthropods that use the corpse as an extension of their normal habitat • Hunting spiders
The Blow Fly Black • Acts as both necrophages and as a predator. • One of the most common species on dead bodies • Often arrive within 10 minutes • Feed on any blood or fluids and then start laying eggs in and around the natural body cavities • If the food source is exhausted, they will prey on other species in the same genus (Chrysomya) Green
Blow Fly continued • Blowflies seek moist areas of the corpse to lay their eggs • The nose, mouth, armpit, groin and open wounds are favored locations • Eggs hatch into maggots within 24 hours • Usually reach length of 1cm after 3 days • During the next 6 to 10 days they feed, grow and repeatedly molt • Become a pupae when their outer covering hardens • Approximately 12 days later adult flies emerge