1 Entomology l Review Forensic entomologists study INSECTS

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

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

Insects 101 Vital role in “recycling” carcasses l Only animals to have “true wings” l First to colonize a corpse; do so in a predictable pattern l 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 4

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

Insect Life Cycle 6

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

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

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

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

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 11

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 12

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

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