Maggots and Time of Death Estimation 4/30/2018 Forensic Entomology Chem-195H Maggots and Time of Death Estimation

Entomology is the Study of Insects 4/30/2018 Entomology is the Study of Insects Images from: www.afpmb.org/military_entomology/usarmyento/files/ArmyEntomology.ppt Chem-195H

What is Forensic Entomology? Forensic Entomology is the use of the insects and other arthropods that feed on decaying remains to aid legal investigations.  Medicolegal (criminal) Urban (criminal and civil) “legal proceedings involving insects and related animals that affect manmade structures and other aspects of the human environment” Stored product pests (civil)  4/30/2018 Chem-195H

Medicolegal Forensic Entomology Often focuses on violent crimes Determination of the time (postmortem interval or PMI) or site of human death based on identification of arthropods collected from or near corpses. Cases involving possible sudden death Traffic accidents with no immediately obvious cause Possible criminal misuse of insects 4/30/2018 Chem-195H

Postmortem interval (PMI) Forensic Entomology is used to determine time since death (the time between death and corpse discovery) This is called postmortem interval or PMI). Other uses include movement of the corpse manner and cause of death association of suspects with the death scene detection of toxins, drugs, or even the DNA of the victim through analysis of insect larvae. 4/30/2018 Chem-195H

Forensic Entomology is Applied Biology If it weren’t for decomposition of all living things, our world would fill up with dead bodies. When an animal dies, female insects will be attracted to the body. They enter exposed holes or wounds and lay eggs or larvae. A forensic entomologist: identifies the immature insects determines the size and development of the insects calculates the growth of the insects and passage through stages of the life cycle in laboratory compares the growth against weather conditions to estimate time of oviposition Oviposition means time of laying eggs. 4/30/2018 Chem-195H

Succession of Insects on the Corpse Estimates of postmortem intervals based on insects present on the remains are based on: The time required for a given species to reach a particular stage of development. Comparisons of all insect species present on the remains at the time of examination. 4/30/2018 Chem-195H

Ecology of Decomposition Necrophages - the first species feeding on corpse tissue. Includes rue flies (Diptera) and beetles (Coleoptera). Omnivores - species such as ants, wasps, and some beetles that feed on both the corpse and associated maggots. Large populations of ominvores may slow the rate of corpse’s decomposition by reducing populations of necrophagous species.(are insects/arthropods that feed directly on remains, or the fluids released from remains during the decomposition process) Parasites and Predators - beetles, true flies and wasps that parasitize immature flies. Incidentals – pill bugs, spiders, mites, centipedes that use the corpse as an extension of their normal habitat 4/30/2018 Chem-195H

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Decay Rates Are Variable Most important environment factors in corpse decay: Temperature Access by insects Depth of burial Other Factors Chemical-- embalming agent(preservatives), insecticides, lime, etc. Animals disrupting the corpse 4/30/2018 Chem-195H

Time of Death can be broadly estimated up to about 36 hours Temperature Stiffness Time of death 4/30/2018 Warm Not stiff Dead less than three hours Warm Stiff Dead between 3 to 8 hours Chem-195H Cold Stiff Dead between 8 to 36 hours Cold Not stiff Dead in more than 36 hours

Stiffness/ Rigor Mortis Time of Death Warm 4/30/2018 Body Temperature Stiffness/ Rigor Mortis Time of Death Warm Chem-195H

Differentiate between PMI and Time of Death These may not always parallel. Post mortem interval is restricted to the time that the corpse or body has been exposed to an environment which would allow insect activity to begin. Closed windows Body in box or bag Cold temperatures Deeper burial 4/30/2018 Chem-195H

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Calculating PMI from Accumulated Degree Hours (ADH) To Temp Hours ADH Cumulative ADH Egg 1st Instar 70° F 23 23 x 70= 1610 ADH 1610 2nd Instar 70 ° F 27 27 x 70= 1890 ADH 1610+ 1890 3rd Instar 22 22 x 70= 1540 ADH 1610+1890+ 1540 Pupa 130 130 x 70= 9100 ADH 1540+9100 Adult Fly 143 143 x 70= 10010 ADH +10010 4/30/2018 Chem-195H 24100 ADH

Using the Data 3928 ADH in these three days (952+1488+1488). How many ADH of 70º are there in these 3 days? 3928/70=56.11 hours 72 hours at 70º would have the insects passing to the 3rd instar. But 72 hours at colder temperatures and insects will only be at 2nd instar stage. 4/30/2018 Chem-195H

Five Stages of Decomposition Fueled by Insect Activity. Fresh Bloat Decay Post-decay Dry (skeletal) 4/30/2018 Chem-195H

Fresh Begins at death Flies begin to arrive 4/30/2018 Begins at death Flies begin to arrive Temperature falls to that of the ambient temperature. Autolysis, the degradation of complex protein and carbohydrate molecules, occurs. Chem-195H 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.

Bloat Swells due to gases produced by bacteria Temperature rise of the corpse Flies still present 4/30/2018 Chem-195H

Decay Gases subside, decomposition fluids seep from body. Bacteria and maggots break through the skin. Large maggot masses and extreme amounts of fluid. Unpleasant odor Larvae beginning to pupate. Corpse reduced to about 20% of it’s original mass. 4/30/2018 Chem-195H 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.

Post-Decay Carcass reduced to hair, skin, and bones. Fly population reduced and replaced by other arthropods. Hide beetles are dominant in dry environments. Mite and predatory beetle populations increase. 4/30/2018 Chem-195H 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.