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2 Entomology Review: Forensic entomologists study Based on the life cycle stage of insects, entomologists can determine how long a body has been dead; determines PMI (postmortem interval) INSECTS (true wings)

3 What is Forensic Entomology? Review: Definition The application of the study of arthropods to criminal or legal cases - includes spiders, centipedes, blow flies, millipedes, crustaceans

4 Insects 101 Vital role in “recycling” carcasses Only animals to have “true wings” First to colonize a corpse; do so in a predictable pattern Necrophagous insects: insects who eat dead flesh - through the study of taphonomy, scientists can tell how processes such as wind, rain, and insects affect a corpse

5 Insects 101 continued… 6 legs, 3 body segments (head, thorax, abdomen) Nearly 1 million species Have an exoskeleton

6 Insect Life Cycle

7 Collecting Insects at a Crime Scene Only certain insects invade dead bodies - Vary based on environment, time, weather Necrophilious insects can sense chemical changes in decomposing tissue and register it as “food” Attracted to dark, moist areas on body (wounds, nose, mouth, eyes, anal openings) Insects are captured with nets or forceps and put into ethyl alcohol for preservation; labeled; soil samples also taken

8 Postmortem Interval PMI (Postmortem Interval) is the time range for when a crime occurred and how long ago the victim was killed A minimum and maximum time since death are established Extremely hard to establish an accurate maximum PMI because as time/decomposition continues, the more unclear time of death becomes

9 PMI continued… Categorizing insects and classifying them is called the science of taxonomy Insects are named based on their Genus species name Ex. Calliphora vicina (blue bottle fly) PMI is based on ecological and faunal study of cadaver (stages of development of insects on body)

10 Infestation order 1. Necrophagous species: flies that feed off of body 2. Predatory and Parasitic species: beetles, ants, bees, wasps that feed off of the necrophagous species 3. Omnivorous species: beetles, wasps, and ants that feed on both human body and other insects 4. Incidental (Normal) species: spiders and other naturally occurring insects found in the environment

11 Stages of Decomposition 1. Fresh Stage - at moment of death; body temp falls to surrounding temps; blowflies land on body and lay eggs; maggots hatch; predators/parasites also arrive 2. Bloated Stage - bacteria in the body release gas; body is bloated and swollen; temp is very hot; maggot masses bigger; body fluids seep out of body

12 Stages of Decomposition 3. Decay Stage - skin of corpse begins to crack; gases escape; lose bloated appearance; strong foul odor; more beetles arrive 4. Post-Decay Stage - not much of body left except bones, cartilage, skin, and hair; new kinds of beetles; mites infest soil below body

13 Stages of Decomposition 5. Skeletal Stage - only bones and hair are left; no more insects left on skeleton

14 Other Information on Insects Insects can provide DNA of the victim by removing the waste inside the insect Insects can also provide drug/chemical evidence because they are feasting on the tissues of the body Insects can also indicate location, travel, and geography of a victim