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Entomology is the Study of Insects

Entomology is the Study of Insects. Forensic Taphonomy. Reconstructing the circumstances of death . Estimating the time of death. What is Forensic Entomology?. The use of insects and their arthropod relatives that inhabit decomposing remains to aid legal investigations.

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Entomology is the Study of Insects

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  1. Entomology is the Study of Insects

  2. Forensic Taphonomy • Reconstructing the circumstances of death • Estimating the time of death

  3. What is Forensic Entomology? • The use of insects and their arthropod relatives that inhabit decomposing remains to aid legal investigations.

  4. Insects and other arthropods can be used to answer: Forensic Entomology How or where a death occurred. When did death occur? Postmortem Interval (PMI): Time between death and discovery of a corpse.

  5. Three Areas of F. Ent. • Medicolegal - focuses on the criminal component of the legal system and deals with the necrophagous (or carrion) feeding insects that typically infest human remains • Urban Pests- deals with the insects that affect man and his immediate environment. The damage caused by their mandibles (or mouthparts) as they feed can produce markings and wounds on the skin that may be misinterpreted as prior abuse. • Stored product pests- commonly found in food and the forensic entomologist may serve as an expert witness during both criminal and civil proceedings involving food contamination.

  6. The History of FE • In 1235 A.D., Sung Tz'u, a Chinese "death investigator," demonstrated knowledge of blow fly activity on bodies relative to those orifices infested, the time of such infestation, and the effect of trauma on attractiveness of tissue to such insects. • Francesco L. Redi(1668) • Bergeret (1855), near Paris, France, was the first westerner to use insects as forensic indicators. • Between 1883 and 1898, J. P. Megnin in France published a series of articles dealing with medicocriminal entomology.

  7. Most commonly called upon to determine the postmortem interval or "time since death" in homicide investigations. Use a number of different techniques including species succession, larval weight, larval length, and a more technical method known as the accumulated degree hour technique which can be very precise if the necessary data is available. Make inferences as to possible postmortem movement of a corpse. Freezing or wrapping of the body may be indicated by an altered species succession of insects on the body. Determine the circumstances of abuse and rape. The insects recovered from decomposing human remains can be used for toxicological analysis Why Call a Forensic Entomologist?

  8. Forensic Entomology Review Definition of Forensic Entomology: Study of insects and their arthropod counterparts that interact with legal matters. What is an arthropod? What is an insect?

  9. Insects Insects are a class of Arthropods that have three segments to their body, one pair of antennae, three pairs of legs, compound eyes and breathe air via small holes or spiracles along the side of their body.

  10. Insects Most arthropods are insects BUT there are also bugs that are NOT insects such as spiders (Arachnida), crayfish & woodlice (Crustacea) and millipedes & centipedes (Diplopoda & Chilopoda - sometimes collectively known as Myriapoda). It is easy to be confused!

  11. Insects Classification of the arthropods can also be slightly different in various information sources. To make it even more confusing, as more research is done, scientists may revise or even change what group various organisms belong in.

  12. Insects As you watch the slide presentation, think about the following: Are there ‘good or bad’ insects? What role do insects play in science? Are insects important in forensic science?

  13. Forensic Entomology Arthropoda (phylum) class - Arachnida (spiders, scorpions) class - Chilopoda (centipedes) class – Insecta (insects) order – Hymenoptera (ants, bees, wasps) order – Blattaria (cockroaches) order – Diptera (flies) order – Coloeoptera (beetles)

  14. 1. Blowflies Blow fly eggscan provide investigators with an accurate estimate of postmortem interval (PMI) and allow investigators to narrow their focus Maggots  Growth takes several days to several weeks depending upon species, environmental conditions, and the number of larvae present. Adult Blow-Fly  Differ in abundance from region to region, from habitat to habitat, and from season to season. Important Insects

  15. Forensic Entomology Flies Some flies are attracted to dead bodies. Carrion Flies: • Calliphoridae (blow flies) • Sarcophagidae (flesh flies) • Muscidae (house flies) • Phoridae

  16. Forensic Entomology Phoridae • Scuttle flies or coffin flies • Take advantage of physical barriers; larger flies can’t get to body

  17. Forensic Entomology > Flies Calliphoridae (blow flies) • Shiny color (bluebottle, greenbottle) • Among the first to arrive at a corpse

  18. Green blow fly Phaeniciasericata Joseph Berger, www.insectimages.org

  19. Forensic Entomology > Flies Sarcophagidae (flesh flies) • Large, gray flies • Also among the first flies to arrive

  20. Flesh fly Sarcophagidae - Family Courtesy Ian Dadour, UWA

  21. Forensic Entomology > Beetles

  22. Forensic Entomology > Beetles Coleoptera (beetles) Arrive early or late in decomposition process, depending on species

  23. Carrion beetle Oiceoptomanoveboracensis David Cappaert, www.insectimages.org

  24. Hide beetle Trogidae Courtesy Ian Dadour, UWA

  25. Forensic Entomology > Flies and Beetles Complete Metamorphosis Eggs Larvae Pupae Adult

  26. Smooth & Hairy maggots Courtesy Ian Dadour, UWA

  27. Image: http://www.nlm.nih.gov/visibleproofs

  28. Estimating the PMI Once insects are collected (both adults and immature), they are used to estimate the postmortem interval (PMI).

  29. Estimating the PMI Collection of Insect Samples • Can be collected at the crime scene • Can be collected during autopsy

  30. For each maggot mass: Estimating the PMI > Collection Kill ½ of the maggots collected: • Stops growth for age estimation • Preserve in ethanol or Kahle’s solution • Preservation prevents bacterial degradation Collect Climatological Data: • Environment affects growth rate • Collect temperature, humidity, etc.

  31. For each maggot mass: Estimating the PMI > Collection Keep ½ of the maggots alive: • The species of maggots can not be identified (maggots look the same) • If maggots are raised to adults, the flies can be identified to the species level. Chrysomya megacephala ?

  32. Estimating the PMI Analysis of Insects Once evidence is received, the first step is to identify the species of samples.

  33. Identification of Insects Estimating the PMI > Species Identification Question: Why is species identification important? Answer: Different species grow at different rates 7-mm maggot may be anywhere from 3 days old to 10 days old, depending on species

  34. Estimating the PMI > Species Identification Timeline: Egg Larvae Pupa Adult Sarcophagid bullata 50 hours 110 hours Sarcophagid cooleyi 40 hours 90 hours

  35. Identification of the specimen Estimating the PMI > Species Identification Morphology • Color, hairs and bristles, wing structure • Male genitalia DNA identification • Mitochondrial sequence of the gene region cytochrome oxidase I

  36. After evidence is collected and identified, there are two methods for estimating the PMI: Estimating the PMI > Analysis • Succession of insect fauna • Estimating the age of immature insects

  37. Facts: Estimating the PMI > Analysis > Succession • The corpse provides an attractive environment for insects to feed, mate, and deposit eggs. • The corpse passes through relatively predictable stages of decomposition. • Different species of insects will be attracted to the corpse at different times.

  38. Most flies arrive early in the decomposition process. Estimating the PMI > Analysis > Succession Calliphoridae (blow flies) Sarcophagidae (flesh flies)

  39. Beetles can arrive early or late in the decomposition process (species dependant). Estimating the PMI > Analysis > Succession Coleoptera (beetles)

  40. Conditions affecting succession: Estimating the PMI > Analysis > Succession • Temperature (hotter = faster) • Geographic region (variable insect fauna) • Other factors: wrapped body, buried, indoors, etc.

  41. Since eggs are rarely deposited on a corpse before death… Estimating the PMI > Analysis > Age of Immature Insects The age of immature insect specimens is the absolute minimum amount of time a person has been dead. For example: A three-day-old maggot on a corpse would indicate the body has been dead for at least three days.

  42. Remember, flies and beetles undergo complete metamorphosis Immature specimens = egg, maggot, pupa Estimating the PMI > Analysis > Age of Immature Insects

  43. Estimating the PMI > Analysis > Age of Immature Insects Eggs Larvae Pupae Adult The first step in age identification is to identify what stage the insect is in.

  44. Estimating the PMI > Analysis > Age of Immature Insects If the samples are maggots, the molting stage can be identified. Larvae • Larvae grow in three stages called instars. • During the 3rdinstar, maggots will stop feeding, leave corpse, and pupate.

  45. Instar can be determined by looking at spiracles. Estimating the PMI > Analysis > Age of Immature Insects

  46. Estimating the PMI > Analysis > Age of Immature Insects • 3 “footballs” = 3rd instar • 2 “footballs” = 2nd instar • Glob = 1st instar

  47. Phaeniciasp Spiracles are complete Third-instar larvae

  48. Phormiaregina Spiracles are incomplete Third-instar larvae

  49. Five Stages of Decomposition Fueled by Insect Activity. Fresh Bloat Decay Post-decay Dry (skeletal) CRIME SCENE CREATURES

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