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Presentation on theme: "Entomology."— Presentation transcript:

1 Entomology

2 Introduction Entomology is the study of insects
Forensic entomology is the study of the insects associated with a dead body Also known as medicolegal Forensic entomologists are called into homicide investigations when time of death is unknown and their evidence is usually presented in court as expert testimony

3 Introduction Insects begin colonizing at a dead body immediately after death Dependent on season and environment Rate of development of the species can be used to estimate time since death Can give an estimate up to a year

4 Introduction Entomological evidence is the most accurate and frequently the only method available to determine the elapsed time since death Due to rigor, algor, and livor mortis being useless after 72 hours

5 Introduction Insects are also used to
Determine whether the body has been moved after death Determine whether it has been disturbed Determine the presence or position of wound sites Determine whether the victim used drugs or was poisoned Determine the length of time of neglect or abuse in living victims

6 Importance of Determining Time Since Death
Important for the family of the deceased Understanding how, when, and why a person has died can help to give closure to family and friends and allow them to move on with their lives

7 Importance of Determining Time Since Death
Timing of death may also have legal implications Insurance policies Whether death occurred before or after insurance coverage began Important for families when money is involved

8 Importance of Determining Time Since Death
May indicate the length of time that a fraud has occurred Receiving monies for family members while family members are deceased

9 History of Entomology Is one of the oldest forensic sciences used in death investigations First recorded use was in 13th century China Modern use of entomology in criminal investigations began in France in the mid 1800s First reported use of forensic entomology in North America was in Quebec in 1897 Did not become common until 1970s

10 History of Entomology American Board of Entomology was established in 1996 by Dr. Paul Catts and Dr. Lee Goff European Association of Forensic Entomology was established in 2001

11 Training Must have extensive training in entomology
Bachelors degree in biology, zoology, or entomology Masters in entomology PhD in forensic entomology, insect ecology, and taxonomy Board certification requires 5 years of experience after PhD Most forensic entomologists are university professors


13 Employment Forensic entomologists do not work full time for crime labs
Primary employment is in research and teaching Therefore, most have little or NO experience with crime scenes, legal report writings, or court testimonies

14 Decomposition Begins at the moment of death, caused by two factors
Autolysis The breaking down of tissues by the body's own internal chemicals and enzymes Putrefaction The breakdown of tissues by bacteria These processes release gases that are the chief source of the characteristic odor of dead bodies These gases swell the body

15 Decomposition Scavengers play an important role in decomposition
Insects and other animals are typically the next agent of decomposition, if the body is accessible to them The most important insects that are typically involved in the process include the fleshflies (Sarcophagidae) and blowflies (Calliphoridae) The green-bottle fly seen in the summer is a blowfly Larger scavengers, including coyotes, dogs, wolves, foxes, rats, and mice may eat a body if it is accessible to them Some of these animals also remove and scatter bones.

16 Factors Involved in Decomposition
In a roughly descending degree of importance, those factors include: Temperature The availability of oxygen Prior embalming Cause of death Access by insects Burial, and depth of burial Access by scavengers Trauma, including wounds and crushing blows Humidity, or dryness Rainfall Body size and weight Clothing The surface on which the body rests


18 Determination of Elapsed Time Since Death
First method based on the predictable development of larval Diptera, known as the blow fly Used from the first time the first egg is laid on the remains until the first adult flies emerge from the pupal cases and leave the body Evidence valuable from a few hours to several weeks after death

19 Determination of Elapsed Time Since Death
Second method is based on the predictable, successional colonization of the body by a sequence of carrion insects Can be used from a few weeks after death until nothing but dry bones remain



22 Blow Flies Blow flies are the first flies to be attracted to a body
They are large, metallic flies seen near food or garbage cans in summer Blow flies belong to the family Calliphoridae, in the order Diptera or “true flies”


24 Blow Flies Male and female blow flies require a protein meal before the ovaries and testes develop and oogenesis and spermatogenesis can occur Adult feeding may occur at the dead body Majority of the flies attracted to remains are females searching for egg laying sites


26 Blow Flies Blow flies develop from eggs through the first, second, and third instar stages, and then the pupal stage before becoming adults Stages influenced by species of blow flies and temperature of surroundings

27 Blow Flies Insects are cold-blooded so their development is temperature dependent As temperature increases, they develop more rapidly As temperature decreases, they develop more slowly

28 Blow Flies Analysis of the oldest insect stage on they body, together with knowledge of the meteorological conditions at the scene, can be used to determine how long insects have been feeding on the body, and hence, how long the victim has been dead

29 First Instar Stage Once blow fly eggs have been laid, they will hatch into first instar larvae Larvae rely on protein for their meals Females lay eggs on open wounds of dead individuals or around orifices of a living individual Face is colonized before other areas because the skin is easier to penetrate Except in the case of rape cases, flies attracted to genetalia

30 Second Instar Stage First instar larvae shed larval cuticle and mouthparts when entering second instar stage Is more capable of penetrating the skin than the first instar larvae Does so with proteolytic enzymes

31 Third Instar Stage Third instar stage begins with second instar larvae shedding its cuticle Are called maggots Maggots aggregate together in large masses Can remove a large amount of tissue in a very short amount of time After feeding, the maggots move on to a site where they can pupate Remove outer cuticle so they can emerge as a fly



34 Time Span Female lays 2,000 eggs in her lifetime
Once eggs are laid, they hatch between 12 and 48 hours It takes 14 days for the fly to emerge from the pupal case


36 Factors Used to Determine Time Since Death
4 factors must be taken into account Oldest stage of blow fly associated with the body Look at old pupal cases Species of insects Each species develop at different rates so each species of insects at the scene need to be collected Temperature data Must be able to determine temperature of crime scene for a period of time Developmental data Must know how fast or how slow the specific species develop

37 Determining Whether the Body has been Moved
Insects present on the deceased body that are not prevalent to the crime scene can indicate that the victim was murdered elsewhere and was dumped at another location

38 Presence and Position of Wounds
Insects are attracted first and foremost to wounds so the first instar larvae will have access to liquid protein for nutrition Wound sites in individuals that have completely decomposed are shown by irregular or atypical insect colonization

39 Linking Suspect to Scene
Sometimes, criminals carry entomological evidence on them unknowingly This evidence can place them at the crime scene by examining the life cycles of the insects

40 Drugs Insects that feed on the body of individuals that have been poisoned can be examined to determine what type of drug or toxin the person was poisoned with It is important to note that specific drugs either speed up or slow down larval development Can influence entomologist’s final report

41 Collection of Entomological Evidence
Evidence should be collected by an entomologist If not available, a police death investigator should collect the evidence Different stages of larval growth should be collected and bagged separately Sample of soil should also be collected from just outside the area marked by body fluids

42 Challenges to Forensic Entomology
3 challenges exist Temperature Temperature of crime scene and the temperature that the insects have been exposed to us unknown Season Entomology is valuable only in spring, summer, and fall Exclusion of insects Insects are excluded based on condition of body

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