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Chapter 11 Forensic Entomology By the end of this chapter you will be able to: 11.1 Describe several examples of the ways that forensic entomology is used to help solve crimes. 11.2 Compare and contrast the four stages of blowfly metamorphosis, and describe the significance of blowflies in forensic entomology. 11.3 Describe the function of each of the following organs on blowflies and explain the significance of each structure to forensic entomology: spiracles, mouth hooks, crop. 11.4 Describe the effect of different environmental factors on insect development. 11.5 Describe the five stages of decomposition.

Chapter 11 Forensic Entomology By the end of this chapter you will be able to: 11.6 Relate the process of insect succession to the changing environment that occurs during the stages of decomposition. 11.7 Explain how forensic entomologists interpret forensic evidence and environmental conditions to estimate a postmortem interval. 11.8 Explain how insect evidence is analyzed to provide evidence of the deceased person’s identity or drug, poison, or toxin exposure. 11.9 Summarize the procedures for documenting and collecting insect evidence from a crime scene.

Chapter 11 Vocabulary accumulated degree hours (ADH) complete metamorphosis crop entomology forensic entomology grub insect succession instar larva maggot oviposition pupa spiracles

Introduction Insects have 3 body segments: Head Thorax Abdomen

Introduction (continued) Forensic entomology uses insect evidence in civil and criminal investigations. Adults Nymphs Pupae Larvae Eggs Insect body parts

How is Forensic Entomology Used? Insect evidence can be used to: Locate a body Determine if the body was moved Identify a geographic range of the crime Link a suspect to a crime Indicate where a suspect had been traveling Trace the origin of drugs

Forensic Entomologists Forensic entomologists may answer the following questions: Where on the body were the injuries? Was the body moved after death? Was the victim restrained while alive? Was the body covered, buried, or submerged in water? Was the deceased exposed to any toxic chemical or under the influence of recreational drugs?

History of Forensic Entomology In 1247, The Washing Away of Wrongs describes how flies were used to identify a bloody murderer. In 1855, insect evidence was used to solve the death of a murdered infant hidden in the wall of a house. In the early part of the 20th century, research done on the effect screwworm flies had on living cattle and sheep laid the groundwork for future entomologists.

Insects and Decomposition A decomposing body follows a regular pattern and predictable changing habitats. The stages include: Fresh Bloated Decay Active decay Dry, or skeletal, decay These different habitats support the predictable sequence of insect succession on a dead body.

Blowflies (Bottle Flies) When putrescine and cadaverine are released by decomposing tissue, blowflies are alerted to potential locations to lay their eggs. After feasting on the protein-rich fluids from a decomposing body, female flies deposit their eggs in clusters on the body.

Growth and Development During the complete metamorphosis of blow flies, the following stages occur: Egg Larva Pupa Adult

Morphology (Body Shape) Blowfly larvae use hooks to dig and scrape at decomposing flesh to move the flesh toward the mouth.

Morphology (Body Shape) (continued) Spiracle configuration alerts investigators to the developmental stage of the instar.

Morphology (Body Shape) (continued) An empty pupal case signals that a body has been in an area long enough for the blowfly to complete its full lifecycle.

Houseflies, Flesh Flies, and Coffin Flies

Beatles and Other Insects of Decomposition Beetles follow a predictable path of insect succession on a decomposing body.

Estimating Postmortem Interval Blowfly Importance Factors Affecting Development Temperatures and environmental conditions Degree Hours Accumulated degree hours (ADH) is the number of hours at an adjusted average Celsius temperature than it takes an insect species to reach a particular stage of development.

Processing a Crime Scene for Insect Evidence Death-Scene observations Collection of Meteorological Data Two Collections: Collect live insects, and collect and preserve other insects from the body at the crime scene. After Body Removal: Collect insects from the surrounding soil.

Summary Insects, the most numerous of all animals, provide valuable evidence in solving crimes. Forensic entomology is used to estimate postmortem intervals, identify the geographic location of the crime scene, link a suspect to a victim or crime scene, determine if a body was moved, locate injury sites, determine exposure to drugs or toxins, and provide evidence of neglect or abuse. The five stages of decomposition include fresh, bloated, active decay, advanced decay, and dry decay; stages of decomposition cause predictable changes in the chemical and physical environment of a body and the area surrounding it.

Summary (continued) Forensic insects include flies, beetles, wasps, ants, and more. Insects follow a predictable sequence of inhabiting a dead body, known as insect succession. Blowflies, usually the first to inhabit a dead body, undergo four stages of complete metamorphosis: egg, larva (first instar, second instar, third instar), pupa, and adult. Larvae use mouth hooks to help ingest food and move, a crop to store food, and spiracle slits to breathe.

Summary (continued) Beetles usually arrive after flies and may consume the dead body or consume eggs and larvae found on the body. Variables affecting the rate of insect growth include temperature, sun, shade, wind, moisture, injuries to the deceased, and a body that is clothed or wrapped. All must be considered when a forensic entomologist interprets insect evidence. The postmortem interval is an estimate of the interval of time between when the body was found and death.

Summary (continued) Accumulated degree hours (ADH) are the number of hours at an adjusted average temperature it takes for an insect species to develop to a given developmental stage. ADH are used to estimate postmortem intervals. Evidence collection includes crime-scene observations, collection of live insects and eggs, preserving insects, and collection of meteorological data.