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Forensic Entomology

Explore the science of using insects and arthropods to solve legal issues, including estimating time of death and insect succession. Dive into the study's subfields and practical applications. Learn about common insect species and their life cycles in forensic investigations.

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Forensic Entomology

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  1. Forensic Entomology

  2. Overview of presentation: • What is forensic entomology? • Medicocriminal entomology. • 3. How long has a particular individual been dead? • A. Developmental times of insects. • B. Insect succession. • 4. Description of a project being conducted at ASU.

  3. What is Forensic Entomology? The study of insects and other arthropods to legal issues. Broad field. It can be divided in three subfields: 1. Urban Forensic Entomology 2. Stored-product Forensic Entomology 3. Medicocriminal Entomology

  4. Medicocriminal entomology usually involves: 1. The intrigue surrounding human or animal death. 2. The decay process. 3. Detective work necessary to bring perpetrators to trial.

  5. A typical question posed to a medicocriminal entomologist: How long has a particular individual been dead? Estimates of time a decedent has been dead “PMI” = Postmortem Interval. Involves application of the temperature-dependent development of insects.

  6. Insect Succession • One important biological phenomenon that occurs on cadavers are a succession of organisms that thrive on the different parts. • Flies lay eggs usually within the first 24 hours • Predatory rove beetles or parasites that feed on maggots will have to wait until the blow flies arrive and lay their eggs. • Beetles that specialize on bone, will have to wait until bone is exposed. • The succession on cadavers happens in a fairly predictable sequence and can be used in estimating time of death if the body has been lying around for some time.

  7. Show: YouTube: Maggots feast on animal carcass

  8. ORDER DIPTERA Commonly called flies. Over 86,000 known species, over 16,000 occur in North America. One of the largest insect orders. Found in almost every habitat. Complete metamorphosis. Body characteristics: One pair of wings. Second pair of wings reduced to knob-like organs called HALTERES (used to stabilize flight). Compound eyes. Mouthparts vary (sponging, piercing, cutting- sponging)

  9. Pseudotrachea Flies associated with carrion have SPONGING mouthparts

  10. The Life Cycle of a Fly Adults Larvae 3 instars Prepupal stage Exact time depends on temperature and moisture Pupae

  11. Pupae are cylindrical. Posterior spiracles also present (used for identification).

  12. Developmental Data on Blow Flies and Flesh Flies 27°C and 50% humidity

  13. Blow Flies (Family Calliphoridae) Extremely large family of medium-sized flies. ~1,000 spp., found worldwide. Along with sarcophagid and muscid flies, the most important species that provide information relating to accurate estimation of the postmortem interval. Attracted to carrion and excrement, with some exploiting open wounds. First to arrive at a crime scene. YouTube: “Maggots feast on animal carcass”

  14. Black Scavenger Flies (Family Sepsidae) Worldwide in distribution with at least 240 spp. Adults are small, shining black, purple, or red flies. No more than 3.5 mm in length. Head is noticeably rounded. There is a constriction at the base of the abdomen. Behavior: Flick their wings outward as they walk (“waggle flies”).

  15. Beetles (Order Coleoptera) Largest order containing a third of all known insects (300,000 spp.). 30,000 spp. found in N. America. Complete metamorphosis (egg, larvae, pupae, adult). Characteristics: ELYTRA – Front wings hard; covers and protects the hind wings (membranous) that are used for flight. Adults: Chewing mouthparts Most can fly Feeding habits vary: Predacious, Scavengers, Herbivores

  16. Carrion Beetles, Family Silphidae Large family, nearly worldwide in distribution. 1,500 spp. worldwide; 46 spp. in N. America. Medium sized to large beetles (10 to 35 mm). Antennae are clubbed. Elytra are often short and leave several abdominal segments exposed. Body is usually black, marked with orange, yellow or red patches.

  17. Larvae vary in size and shape. Generally 15 to 30 mm long. Most are flattened. All larvae are capable of mobility.

  18. Clown Beetles, Family Histeridae Large family with over 3,000 spp. 500 spp. in North America. Small, seldom larger than 10 mm in length. Round bodies and very shiny. Elytra are short and squared at the apex. Last two abdominal segments are exposed. Antennae: Elbowed and clubbed.

  19. Clown beetles are very common on carrion and excrement (found on fungi and decaying vegetable matter). On a carcass, tend to be concealed in the soil underneath the body during the daylight hours. Most active at night. Both adults and larvae are predacious feeding on maggots, fly pupae and dermestid larvae. When collected, must be separated from other insects.

  20. Skin Beetles, Leather Beetles, Hide Beetles, Carpet Beetles & Larder Beetles, Family Dermestidae Given their names according to their food preferences. Worldwide in distribution with over 500 spp. 123 spp. found throughout North America. Small beetles ranging from 2 to 12 mm in length. Oval in shape, covered with scales (many colorful patterns). Feed on various types of dried animal tissue.

  21. Larvae: Range from 5 to 15 mm Usually covered with long tufts of dense hair Larva Pupa Adults

  22. Approximate duration of each stage of decomposition (in days) of pig carrion in sunny and shaded areas. Advanced Decay Decay Sun Shade Bloat Fresh 0 2 4 6 8 10 12 14 16 18 20 22 24 340 Time Since Death (Days)

  23. Days 1 2 3 4 5 6 7 8 9 10 11 12 13 14 16 18 20 22 28 3-6 mons. 6-9 mons. 9-12 mons. Time Blow fly larvae Rove beetle adults Hister beetles adults Parasitic wasps Rove beetle larvae Hister beetle larvae Dermestid adults Dermestid larvae Insect Succession During One Year

  24. Occurrence Matrix Time since Death (Days) A = Adult L = Larva

  25. An Easy Science Project For Students Objectives: To examine insect succession on chickens that have been placed in a field at the ASU farm complex. Students were responsible for designing and doing the experiment.

  26. Materials and Methods This experiment was conducted from 18 September – 12 October 2007. Dead chickens were donated from a poultry producer in the area. Four chickens were used in this experiment (weighed 8-10 lbs). Chickens were placed in cages to prevent scavenging by other animals. Cages could be opened from the side and top for easy access.

  27. A rock was placed on each cage to prevent the cage from being moved by predators. Two cages were placed next to trees. Two cages were placed in a more open environment. Vegetation around the cages was identified. The amount of sun exposure during the day was also estimated for each cage.

  28. Insects were collected on a daily basis for the first two weeks of the study. After two weeks, insects were collected every other day. Insect collecting techniques used: Aerial nets Forceps Hands Collecting jars Vials with alcohol Insects will be identified to species.

  29. Insects Collected Blow flies – Adults and larvae

  30. Sepsis sp. Ants Rove beetles Dermestidae Flesh flies

  31. Forensic Entomology Little research on forensic entomology in AR Formulate conclusions Develop a hypothesis Analyze the results Design the experiment Test the hypothesis

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