Forensic Entomology Use of Insects that inhabit decomposing remains for legal investigations

Insect Biology Insects-most diverse and abundant forms of life on earth. There are over a million described species- more than 2/3 of all known organisms more total biomass of insects than humans. Insects undergo metamorphosis (Egg to larva to pupa to insect) Larva have a soft tubular body and look like worms. Fly species larvae are “maggots”

What is Forensic Entomology? –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)

Postmortem interval (PMI) Forensic Entomology is used to determine (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.

Differentiate between PMI and Time of Death Not always equal 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

Blow Flies Most useful species to Forensic Entomologists Usually the first to arrive Females lay their eggs around body openings –Nose, mouth, ears, eyes, genitals, wounds

5 Stages of Development 1.Eggs –2mm in length, last about 1 day 2.Larvae –1 st instar, 5mm after 1.8 days –2 nd instar, 10mm after 2.5 days –3 rd instar, 17mm after 4-5 days –Feed on flesh 3.Prepupae –3 rd instar moves away from body –12mm, seen 8-12 days after eggs deposited 4.Pupa –Darkens with time, looks like rat droppings –9mm, seen days after eggs deposited –If empty cases are seen, person has been dead about 20 days 5.Adult –Appear metallic green or blue

Beetles Larvae of beetles very different Larvae have 3 pairs of legs Range from white, fat and hairless to dark brown, thin, and hairy –Many are black with plates on back Skin beetle larvae found in later stages of insect succession –Used in museums to clean bones Rove beetles, sexton beetles, and carrion beetles eat maggots –Sexton beetles are nocturnal and usually found under the body or in the soil

Cockroaches Have strong mandibles and can produce damage to skin that resembles abrasions or chemical burns Can consume hair Most common species are American, Australian, and German cockroaches

Other Organisms Red-tailed flesh fly –Skip egg stage –Less numbers of them, but larger in size Bronze dump fly –Found on remains with fecal material or exposed gut Greenbottle blow fly –Found in southern US –Larvae live in moist habitats Hairy maggot blowfly –Larvae consume other larvae –Sometimes the only insect recovered on bodies in southeastern US

Circumstances of Death Sites of infestation –Wounds –Genitoanal region – sexual crime Toxicology evidence –Sample from maggots, empty puparia, or larval skin cast to test for chemicals

Collecting Entomological Evidence Written and photo documentation should always be made

At the Crime Scene Habitat dictates what type of insects could be found Estimate number and kinds of flying and crawling insects Locations of major infestations Insect predation Exact position of the body –Part that are in contact with substrate –Where sunlit and shaded on the body during a day Insect activity 3-6 m from the body Note anything that could alter environmental effects on the body

Climatological Data Insect life is determined by temperature and humidity The following should be collected from a scene: –Ambient temperature –Ground temperature –Body surface temperature –Under body surface temperature –Maggot mass temperature –Soil temperature after the body is removed Directly under ground cover, 4cm deep, 20 cm deep Weather data should be collected from the nearest meteorological station

Collecting Specimens Passive collection of adults using sticky traps Insect net is used to collect flying insects Eggs, larvae, pupa, and adults on the surface of the body should be collected and preserved Live specimens should also be obtained and placed on rearing medium Insects within the body should be collected at autopsy

Back at the Lab Live specimens should be placed in incubators with known temperature and humidity levels Pictures should be taken to document changes Each species of insect should be determined Experiments outdoors near the crime scene may be necessary for environmental conditions

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

Fresh 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.

Bloat Swells due to gases produced by bacteria Temperature rise of the corpse Flies still present

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

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.

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 nabid and reduviid insects. The corpse is reduced to at least ten percent of the original mass. In the last stage (Skeletal Stage), only bone and hair remain.

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