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Insects in Forensic Science

Insects in Forensic Science. How bugs Tell Time. History. Sung Tz ’ u . 洗冤集錄 ( The Washing Away of Wrongs): This was the first forensic case ever reported (1247AD). Death of a farmer was exposed by blow flies. History (cont ’ d).

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Insects in Forensic Science

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  1. Insects in Forensic Science How bugs Tell Time

  2. History • Sung Tz’u. 洗冤集錄 ( The Washing Away of Wrongs): • This was the first forensic case ever reported (1247AD). • Death of a farmer was exposed by blow flies.

  3. History (cont’d) • Francesco Redi (1688) showed that maggots arise from the eggs not meat. • He disproved spontaneous generation. • He used raw meat in his experiment of covered and open jars.

  4. HOUSE FLY BLOW FLY

  5. Life Cycle • Metamorphosis = transition of insects from egg to adult. • Larvae or maggot • 1st, 2nd. 3rd instar • Pupa • Adult

  6. Life cycle of blow fly

  7. How temp affects metamorphosis: egg to adult blowfly • @ 70oF = normal life cycle • @ 32oF = paused life cycle • @ 90oF = speed up life cycle • OTHER FACTORS • High humidity, uppers (COCAINE), increased 02 will increase life cycle rate by 1 size • Low Humidity, CNS depressant, and decreased 02 can decrease speed (by 1 size) too

  8. Blow Fly Egg

  9. Larvae • Larvae are also called maggots. They emerge 8 -23 hours after egg is deposited. • They feed ONLY on moist dead tissue. • Maggots help to decompose decaying matter. • They are a source of food for other animals – birds and other insects. Head region

  10. Larvae • Each instar in a maggot’s metamorphosis is punctuated by a molt

  11. Adult Blow Fly • Can smell death as far as 10 miles away.

  12. Mouthparts • They can’t bite it’s only a“lapping” mouthpart. • Flies taste with their feet as well as their mouth.

  13. Third Instars -> pupa • The third instar eats voraciously and en masse creating heat. • At the end of 3rd instar, it wanders away from the food source to pupate. To avoid predation. • It burrows several cm. into the soil and forms the pupa (cocoon).

  14. Adults • The adult fly is emerging from the pupa. • The wings/head expand & body hardens • They run and hide quickly.

  15. What feeds on the feeders?

  16. Carrion Beetle • Feed on the larvae of the blow fly. • Sometimes the number of beetles exceed the number of larvae.

  17. WASPS • Feed on adult blow flies, maggots, and carrion beetles but not the corpse • Last to arrive, spiders feed on carrion beetles, and wasps but not maggots or the corpse SPIDERS

  18. SUCCESSION OF INSECTS • DEATH • ADULT BLOW FLIES • CARRION BEETLES • WASPS • SPIDERS • MAGGOTS

  19. THE END

  20. Arthropods also make a contribution to cause of death in area of toxicology • Arthropods may contain drugs or poisons in their body • Dr. Richard Merritt discovered super maggots on a corpse. Person died of overdose of cocaine and caused maggots to feed ravenously and grow abnormally large • ttp://www.exploreforensics.co.uk/forensic-entomology.html

  21. Decomposition Stages • Fresh (1-2 days) – • Adult blow flies, yellowjackets • Bloated (2-6 days)- • Blow flies, yellowjackets • Major Decay(5-11 days)- • Flies, beetles, cockroaches, spiders • After first three stages, liquid has mostly seeped away. Biomass also drastically decreases. • Post-decay(10-24 days)-Beetles, fruit flies, gnats • Dry Stage (24+ days)-Some beetles, ants, and flies

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