2 Forensic Entomology Insects as Evidence Warning: Some material in this presentation and related videos may be too graphic for some people.Forensic EntomologyInsects as Evidence/
3 What do they do?Forensic entomologists apply their knowledge of entomology to provide information for criminal investigations.A forensic entomologist’s job may include:Identification of insects at various stages of their life cycle, such as eggs, larva, and adults.Collection and preservation of insects as evidence.Determining an estimate for the postmortem interval or PMI (the time between death and the discovery of the body) using factors such as insect evidence, weather conditions, location and condition of the body, etc.Testifying in court to explain insect-related evidence found at a crime scene.Did you know? Maggots can be used to test a corpse for the presence of poisons or drugs. Some drugs can speed up or slow down the insect’s development.
4 Insects as EvidenceForensic entomologists use their knowledge of insects and their life cycles and behaviors to give them clues about a crime.Most insects used in investigations are in two major orders:1 – Flies (Diptera) and2 – Beetles (Coleoptera)Blow FlyCarrion BeetleSpecies succession may also provide clues for investigators.Some species may to feed on a fresh corpse, while another species may prefer to feed on one that has been dead for two weeks.Investigators will also find other insect species that prey on the insects feeding on the corpse.Images: Top Right - Chart -
5 Examples of Diptera (Flies) Early Stage DecompositionBlow & Greenbottle Flies(Calliphoridae)Metallic thorax and abdomenFlesh Fly(Sarcophagidae) Striped thoraxLife Cycle of a Calliphoridae FlyLate Stage DecompositionHouse Fly(Muscidae)Cheese Skipper(Piophilidae)Informational Source: Images: Top Left - Middle-Left: Top Right - Bottom -
6 Examples of Coleoptera (Beetles) Early Stage DecompositionEarly to Late Stage DecompositionRove Beetles(Staphylinidae)Predator of fly eggsClown Beetles(Histeridae)Predator of fly eggsCarrion Beetles (Silphidae) Adults & larvae feed on fly larvaeLate Stage DecompositionHam & Checkered Beetles (Cleridae) Predator of flies & beetles;also feed on dead tissueHide Beetles (Scarabidae) Usually the last to arriveSkin Beetles (Dermestidae) Feed on dried skin & tissuesInformational Source:Images: &
7 Weather data is also an important tool in analyzing insect evidence from a corpse. Investigators will make note of the temperature of the air, ground surface, the interface area between the body and the ground, and the soil under the body as well as the temperature inside any maggot masses.They will also collect weather data related to daily temperature (highs/lows) and precipitation for a period of time before the body was discovered to the time the insect evidence was collected.Other factors that might affect their PMI estimates:Was the body enclosed in an area or wrapped in a material that would have prevented flies from finding the corpse and laying eggs?a. Was the body (wrapped in a material, in a closed room, exposed to outside conditions, etc.)?Were other insect species present that may have affected the development of the collected species?a. Not all fly species are found everywhere, and this can provide important information also. For example, the skipper fly, Piophila nigriceps (pie-oh-FEEL-ah NYE-greh-cehps), is found only in urban settings. House flies, blow flies, and flesh flies can be found in both urban and rural settings.Were there drugs or other poisons in or on the body that might have affected the larvae’s development?a. A drug like cocaine speeds up development, while some poisons, such as arsenic and glycosides, slow it down.
8 Click the image to view a video about the Body Farm! Did you know…The “Body Farm” in Knoxville, Tennessee is a university research facility to investigate human decomposition under various conditions in order to understand the factors which affect its rate.
9 Blow Fly Metamorphosis Blow flies are attracted to dead bodies and often arrive within minutes of the death of an animal. They have a complete life cycle that consists of egg, larva, pupa, and adult stages.1st – Adult flies lay eggs on the carcass especially at wound areas or around the openings in the body such as the nose, eyes, ears, anus, etc.2nd – Eggs hatch into larva (maggots) in hours.3rd– Larvae continue to grow and molt (shed their exoskeletons) as they pass through the various instar stages.1st Instar - 5 mm long after 1.8 days2nd Instar - 10 mm long after 2.5 days3rd Instar – mm long after 4-5 days4th – The larvae (17 mm) develop into pupa after burrowing in surrounding soil.5th – Adult flies emerge from pupa cases after 6-8 days.AdultPupaEggs3rd Instar Larva1st Instar Larva2nd Instar LarvaIt takes approximately days from egg to adult depending on the temperatures and humidity levels at the location of the body.Image:Information: and
11 MetamorphosisFlies, beetles, and many other insects have complete metamorphosis, which consists of four stages – egg, larva, pupa, and adult.After the adults mate, the females lay eggs onto corpses - usually near natural body openings or wounds.Feeding activity is usually seen in the head region first (mouth, nostrils, eyes, ears), followed by the excretory and reproductive openings. The trunk of the body is invaded much later in the process.The length of the life cycle varies between different fly species and is dependent on temperature.
12 The Maggot The maggot has a pointy end (mouth parts) and a blunt end. a. The posterior segmentof the blunt end containsspiracles that are used forbreathingb. The pointy end is the anterior and has the mouthparts..Diagram courtesy of Dr Ian Dadour,Centre for Forensic Science, UWA
13 The Posterior End of a Maggot Figure 3: A diagram showing a cross-section of the posterior segment of a maggot.A pair of spiracles is shown, each with 3 slits indicating a third stage maggot.Diagram courtesy of Dr Ian Dadour, Centre for Forensic Science, UWA
14 Phormia reginaSpiracles are incompleteThird-instar larvae
15 Phaenicia speciesSpiracles are completeThird-instar larvae
21 Things to Remember …The progression of insect life follows a pattern, and the developmental rates of flies are relatively predictable.The rate of insect development is influenced by temperature because insects are ectothermic (“cold blooded”), which means their body temperatures are largely dictated by the outside temperature. Only when the outside temperature warms an insect’s internal body temperature to its critical level can the insect become active (and eat and grow).As discussed previously:The postmortem interval—the time between death and discovery of the corpse – can be estimated using insect evidence and temperature data along with other factors, such as the presence of drugs in a corpse and conditions related to the corpse itself (wrapped in a material, in a closed room, exposed to outside conditions, etc.).Any drugs present in the corpse at the time of death can affect the rate of maggot development, as they ingest the drug along with the tissue. A drug like cocaine speeds up development, while some poisons, such as arsenic and glycosides, slow it down.Not all fly species are found everywhere, and this can provide important information also. For example, the skipper fly, Piophila nigriceps (pie-oh-FEEL-ah NYE-greh-cehps), is found only in urban settings. House flies, blow flies, and flesh flies can be found in both urban and rural settings.
23 1. Fresh StageBegins at the moment of death and lasts until the body becomes bloated.Blow flies and flesh flies are among the first to find the body.Predatory wasps and beetles may arrive later to feed on the maggots (but not the corpse).Gasses produced by the metabolic activities of the anaerobic bacteria first cause a slight inflation of the abdomen. The carcass may later assume a fully inflated, balloon-like appearance. Adult and larval blowflies in large numbers attracted to fluids seeping from body, normal soil dwelling fauna depart soil because of seepage of fluids; some muscid flies and ants which can feed on larvae and retard maggot activity.
24 Bloat StageBegins when the body becomes inflated due to the production of gases from bacteria that begin to putrefy the body or cause it to decompose.House flies now join the other flies and their maggots form feeding masses that help to liquefy the tissues of the body.
25 Decay Stage Begins when the skin breaks and the gases escape. Maggot masses are large and very active as they grow older and larger.This is the stage of decomposition that smells bad.At the end of this stage, the maggots leave the corpse in search of a place to pupate in the soil.Decay Stage - Black Putrefaction (Days 5-11) -- Decay stage begins when the abdominal wall is broken, allowing gasses to escape and carcass deflates. This process is facilitated by feeding activities of larval flies present on the exposed remains. Adult flies start to leave body, mainly larval mass. Carcass begins to assume a blackened, wet appearance, and most of the flesh will be removed by the maggots. Toward end of this period, carcass will begin to dry and beetles feed on drier tissue. Flies start to pupate. Predatory beetles such as rove beetles and histerids come to feed on other insects.
26 Post-Decay StageMost of the flesh is gone from the corpse, with only cartilage, bone, and skin remaining.This stage is devoid of flies. Some beetles continue to feed on the highly desiccated or dried remains.Postdecay Stage - Butyric fermentation (Days 10-25) -- In dry habitats, remains consisted of dry skin, cartilage and bones. Site for dermestid beetles, histerids, fly pupae, immature and adult rove beetles. In wet habitats, a large quantity of wet, viscous material, termed byproducts of decomposition, was found in the soil under the remains. Site for immature and adult moth flies, sphaerocerid and muscid flies, rove beetles.
27 Dry (Skeletal)Does not always occur especially if corpse is in a wet region.Maggots will stay longer and hide beetles will not appear.In wet environments the hide beetles are replaced with reduviid insects such as the (assassin bug) etc.The corpse is reduced to at least ten percent of the original mass.In the last stage (Skeletal Stage), only bone and hair remain.Dry Stage (Days 25 +) -- This stage is reached when mainly bones and hair remain. Odor is primarily that of normal soil and litter. Some dermestid beetles, histerids, fly pupae, immature and adult rove beetles, normal soil fauna (mites) start to return. Can last several months to even years.
28 Two Different Maggot Generations These are distinguishable by the length and obvious size difference.The photograph was taken at a time consistent with the influx at 132 hours.
31 Let’s give it a try …Click the image above or click here to visit the website at
32 T. Trimpe 2009 http://sciencespot.net/ Crime Solving InsectsWhat happened to Porky?Presentation developed for use with the Crime Solving Insects activity available atImage:T. Trimpe 2009
33 Case Studies For each case: 1 – Review the police report and weather report.2 – Examine & document the collected evidence.Measure the length of the maggots & pupae. Record your data in the chart.Consult the Species Key and the tables on your lab page to determine the various fly species that were found on the corpse and their ages.3 – Use the information from the reports and your examination to answer the questions.
34 Case #1: Oh, Deer!Police Report: The body of a female deer was found behind a fence along a busy two-lane road on the edge of the city limits of Charlotte. Animal Control was called and reported no apparent wounds on the body. It was not hunting season.Weather Report: Daytime temperatures have been fairly consistent for the past three weeks, ranging from 70 to 74º F.Questions:1. Approximately how long has this animal been dead?2. Why are maggots of different ages found in the body?3. Other than temperature, what abiotic (external to the corpse) conditions would you want to obtain from the weather station to help you to be more confident of your time of death estimation?Species & StageSize(mm)Age
35 Case #2: Canine CaperPolice Report: The body of a large pit bull terrier was found inside a walk-in basement at a home in Cary. Maggots were found concentrated in the head and region behind the shoulder. The windows were closed, although the open curtains allowed sunlight to enter, and the air conditioner was set at 72º F.Weather Report: Daytime temperatures have been variable over the past three weeks, ranging from 75 to 94º F. Skies have been sunny.Questions:1. Approximately how long has this animal been dead?2. What effect, if any, do the outside temperatures have on your estimation of time of death in this case?Species & StageSize(mm)Age3. How does the fact that the windows were closed relate to the populations of flies you observed in and around the corpse?4. Do you suspect foul play? Explain.
36 Case #3: Dandy’s DeathPolice Report: The body of a young male horse was found in a pasture in a small town near Wilmington. The autopsy from the vet school reveals that the cardiac glycoside, oleandrin (a powerful heart stimulant), was present in the body. Oleandrin is found in the oleander plant. Oleander is a common ornamental shrub in this area, but none grows within 200 feet of the pasture.Weather Report: Daytime temperatures have been unusually warm over the past three weeks, ranging from 84 to 86º F.Species & StageSize(mm)AgeQuestions:1. Approximately how long has this animal been dead?2. What effect, if any, does oleandrin have on your estimation of time of death?3. What effect, if any, does temperature have on your estimation of time of death in this case?4. Do you suspect foul play? Explain.
37 Case #4: Porky’s PerilPolice Report: The body of a large pot-bellied pig was found in a dense stand of evergreen trees far from any urban area in Buncombe County. Hairs around the pig’s neck were worn away in a band pattern.Weather Report: Daytime temperatures have been average over the past three weeks, ranging from 70 to 73º F. Temperatures in the woods would be approximately 5 degrees cooler due to the lack of sun in the shady environment.Questions:1. Approximately how long has this animal been dead?2. What effect, if any, does temperature have on your estimation of time of death in this case?3. Do you suspect foul play? Explain.Species & StageSize(mm)Age
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