Presentation on theme: "Forensic Entomology Also Included: Maggot Therapy and Taxidermy."— Presentation transcript:
Forensic Entomology Also Included: Maggot Therapy and Taxidermy
Forensic Entomology Relies Strongly on the Following Ecological Concepts ► Developmental time is temperature dependant at the microhabitat level. ► Ecological succession – A corpse will be invaded by a series of different species or insect groups over time. Each species or group changes the microenvironment through its activities which makes it attractive to new waves of organisms and so on.
The Most Common Application Relates to Death Investigations ► Determining PMI – postmortem interval ► Movement of the corpse ► Manner and cause of death ► Association of suspects with the death scene ► Detection of toxins or drugs through analysis of insect larvae
Estimates of PMI Using Insects May Be Based On: ► Period of time for a given species to reach a particular stage of development ► Comparisons of assemblages of insect fauna on corpse at time of examination ► A combination of both above
Most Important Environmental Factors in Corpse Decay* ► Temperature ► Access by insects ► Depth of Burial ► * Based on study of decay rates of 150 human corpses at U. of Tenn.
Ecological Roles of Insects in Decomposition ► Necrophages – species feeding on corpse tissue; mostly true flies and beetles; age determination (larval instar) important for PMI ► Omnivores – insects that feed both on the corpse and associated fauna; ants, wasps and some beetles; may alter rate of decomposition ► Parasites and Predators – many beetles, true flies and wasps that attack immature flies ► Incidentals – use the corpse as a resource extension; springtails, spiders, centipedes, some mites
Five Stages of Human Decomposition Have Been Recognized -1 ► Fresh Stage (Days 1-2) – From moment of death to first sign of bloating; flesh flies, blow flies, ants eating fly eggs and predatory wasps;
Flesh Flies – 2 Species
Two Blowfly Species
House Flies on Dead Host
Five Stages … 2 ► Bloated stage (Days 2-6) – putrefaction begins; gases produced by anaerobic bacteria; considerable bloating; seepage of fluids; adult and larval blowflies attracted in large numbers to seepage; soil fauna moves away due to wetness of earth; ants and other species of flies prey on maggots
Five Stages … 3 ► Decay Stage (Days 5-11) – Abdominal wall is broken and carcass deflates; adult flies begin to leave but great masses of maggots remain and feed; carcass will begin to dry and beetles begin feeding on drier tissue; flies start to pupate; predatory beetles such as rove and hister beetles are attracted
Pig Carcass Infested With Blowfly Maggots
Hister Beetles Prey on Blowfly Larvae
Rove Beetles – 2 Species
Five Stages … 4 ► Postdecay Stage (Days 10-25) in dry habitats - remains consist of dry skin, cartilage and bones; site for dermestid beetles, histerids, fly pupae, immature and adult rove beetles in wet habitats – large quantities of wet, viscous material (byproducts of decomposition) found in soil under the remains; site for adult and immature moth flies, rove beetles
Dermestid Beetles – Adult and Larvae
Five Stages … 5 ► Dry Stage (Days 25+) – Mainly bone and hair is all that remains; odor is primarily that of soil and litter; some dermestids, fly pupae, immature and adult rove beetles, normal soil fauna consisting of mites, etc. start to return; this stage could last for several months to years
Carrion Beetles – 2 Species
Female Carrion Beetle and Kangaroo Rat Rat will be completely buried and eggs laid upon it.
Barriers to Decomposition and Irregular Decomposition ► Physical – soil, water, caskets, antermortem and postmotem injuries ► Chemical – embalming agent, insecticides, lime, etc. ► Climatic – heat, cold, wind, rainfall ► Animals – bird, mice, rodents, canids, cats, etc.
Maggot Therapy – Technically called Maggot Debridement Therapy or MDT Fly larvae are used to scavenge on dead tissue associated with a wound. Fly larvae excrement, termed allantoin has a high ammonia content which appears to serve as an antibiotic.
Wounds on the Battlefield in World War II It has been noted by war surgeons that wounds incurred by troops in which fly larvae were feeding had much less gangrene and healed more quickly than wounds that were protected from flies …
Phaenicia sericata – the green blow fly. This species feeds only on necrotic (decayed) tissue.
Interesting and True … ► Maggot therapy is much more commonly used in Great Britain and Europe than in the U.S. ► There have been about 25,000 treatments in Great Britain since ► Ronald Sherman, M.D. is the pioneer of maggot therapy in the U.S. He is located at U. of Calif., Irvine.
Maggots Feeding at Edge of an Ulcerating Wound on Foot
Maggots Cleaning Up a Wound Associated with an Amputation
Vertebrate Biology/Taxidermy – Skull and Skelton Preparation
A Skull Cleaned by Dermestid Beetles
Trays of Vertebrate Skulls in Dept. Of Vertebrate Biology, Univ. of Michigan
A Great Horned Owl Skeleton
Dermestid Colony Housing
Larval and Adult Dermestids Working on Jawbone
Bear’s Skull Being Cleaned
Dermestid Beetles Are Economic Pests and Will Scavenge on Anything Organic of Both Plant and Animal Origin ► Destroy woolen carpets, upholestry and rugs ► Consume insects on pins in museum and university collections ► Stored furs, leather and skins ► Meat, cheese and stored products ► Materials made of silk
Dermestids are Beneficial in Terms of ► Their use in vertebrate skull/skeleton collections ► Their forensic use as we have seen