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Insect Biology

Insect Biology. Entomology 2. Phylum Arthropoda. Largest phylum on Earth 75% of all living species Class Arachnida (spiders, ticks, scorpions…) Class Crustacea (shrimp, crabs, crayfish…) Class Insecta Class Diplopoda (millipedes) Class Chilopoda (centipedes). Class Insecta.

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Insect Biology

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  1. Insect Biology Entomology 2

  2. Phylum Arthropoda • Largest phylum on Earth • 75% of all living species • Class Arachnida (spiders, ticks, scorpions…) • Class Crustacea (shrimp, crabs, crayfish…) • Class Insecta • Class Diplopoda (millipedes) • Class Chilopoda (centipedes)

  3. Class Insecta • Largest class of animals on Earth • ~800,000 species • Over 200 million per person • History includes over 250,000,000 years of Earth history • Many species still undiscovered • Populate EVERY habitat on Earth • Approximately 90,000 to 125,000 species in North America alone

  4. Class Insecta • 3 body parts • Head • Thorax • Abdomen • 6 jointed legs • 3 pairs on thorax • Exoskeleton • 2 antennae • Compound eyes

  5. Class Insecta • Metamorphosis • Describes the way by which insects change, grow, develop from egg to adult • All insects undergo some type of metamorphosis due to exoskeleton • Referred to as “moults” • Many adults do not feed…adult phase for mating only • Incomplete (12%) • Gradual change over time • Young looks similar to adult • Complete (88%) • 4 distinct stages

  6. Incomplete Metamorphosis • Egg • Nymph • Small adult • Lacks wings • Several stages • Adult

  7. Complete Metamorphosis • Egg • Larva • Worm like • Maggot, Caterpillar… • Molt several times • Pupa • Cocoon • Adult

  8. Order Diptera • “Two wings” • Includes flies of all varieties, mosquitoes, gnats • Many feed on rotting flesh or other decaying matter • Highly in tuned sense of smell is common

  9. Order Diptera • Forewings are membranous • Used for flying • Hindwings are for balancing • “Halteres” – knob like • Metamorphosis-Complete • Mouthparts-sucking (most) • All forensically valuable species

  10. Blow/Bottle Flies Flies usually infest first because larvae (maggots) can survive in the liquid medium of the corpse.

  11. Blow Flies • Kingdom • Animalia • Phylum • Arthropoda • Class • Insecta • Order • Diptera • Family • Calliphoridae • Genus • Cynomyopsis • Species • cadaverina

  12. Medicinal Uses of Maggots • Well documented cases in medicine for centuries • Maggots will selectively eat dead tissue before living tissue • “Maggot therapy” is an accepted method for fighting infections • Now seeing a resurgence due to MRSA*, etc. *Methicillin-resistant Staphylococcus aureus WARNING – GRAPHIC IMAGES

  13. Maggots in leg amputation

  14. Maggots in Wound

  15. Maggots in small cavity wound

  16. Order Coleoptera • “Sheathed wing” • Largest group of insects • 25% of ALL living species • Includes the beetles and weevils • 350,000 known species • Forewings are hard; cover hindwings • Hindwings are membranous • Used for flight • Wings meet in straight line down the middle of the back • Metamorphosis-Complete • Mouth parts-Chewing • Usually eat the fly larvae rather than the corpse

  17. Carrion Beetles • Kingdom • Animal • Phylum • Arthropoda • Class • Insecta • Order • Coleoptera • Family • Silphidae • Genus • Necrophila • Species • americana

  18. Determining Time of Death • Known as Post-Mortem Interval (PMI) • Use insect stage (instar) to determine the time since death • Maggots have 3 instars (or molts) before pupa • Must consider: • Temperature • Time of day • Exposure of corpse (air, soil, water)

  19. PMI Determination • ID species • Different species usually arrive in specific orders based upon senses • Document larval length • Measure maggot size • Determine instar • Can be determined by examining body features • Calculate PMI

  20. Species Identification • Look at structural differences • Body Shape • Color • Texture • Mouth hooks (at tapered end) • Spiracles (at blunt end)

  21. Determine Instar • Look at the Posterior End of maggot • Breathing “spiracles” are located here • Count the number of spiracle slits to determine the instar

  22. Spiracle Slits Spiracles used for breathing by the blow fly larvae.

  23. Mouth Parts Mouth hooks used by blow fly larvae to attach themselves to a food source. As a reminder, the larvae have no legs.

  24. 1st Instar • 0-36 hours after eggs are laid • 2 mm to 5 mm • 0 to 1 spiracle slits

  25. 2nd instar • 36-72 hours • 5 mm to 10 mm • 2 spiracle slits

  26. 3rd Instar • 72 hour + • 15 mm to 20 mm • 3 spiracle slits

  27. Pupa • Pupa cases usually found within a few feet of food source • Cases can last for decades

  28. Establishing Time of Death

  29. Stages of Decomposition Experiment WARNING – GRAPHIC IMAGES

  30. Living Pig

  31. 0 to 3 days Fly Eggs in EAR

  32. 4 to 10 days

  33. 10 to 20 days

  34. 20 to 50 days

  35. 50 to 365 days

  36. Facts! • In warm weather, maggots can digest 60% of a human body in less than a week!

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