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Insects

Insects. Chapter 37. The Insect World. Section 37.1. Three tagmata : Head : mandibles to chew, pair of antennae for sensory Thorax : 3 pairs of jointed legs, most have 1 or 2 pairs of wings Abdomen : 9-11 segments. Characteristics of Insects. Head. Thorax. Abdomen. Exoskeleton with….

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Insects

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  1. Insects Chapter 37

  2. The Insect World Section 37.1

  3. Three tagmata: Head: mandibles to chew, pair of antennae for sensory Thorax: 3 pairs of jointed legs, most have 1 or 2 pairs of wings Abdomen: 9-11 segments Characteristics of Insects

  4. Head Thorax Abdomen

  5. Exoskeleton with… Antennae Examples: Leg Examples:

  6. Appendage examples:

  7. Two types of mouthparts: Sucking Chewing

  8. Entomology: • The study of insects • & other terrestrial arthropods • Person = entomologist • Classify insects into 25 orders based up: • Mouthparts • Number of wings • Type of development

  9. Classification of Insects • Subphylum: Hexapoda • Class: Insecta • Common Orders: • Hemiptera • Homoptera • Isoptera • Odonata • Orthoptera • Coleoptera • Diptera • Hymenoptera • Lepidoptera Table on page 743

  10. Success of Insects • Insects live everywhere (except deep ocean) • 1 million species (more than 3x all other animals!) • 10 million might exist • Why so many? • Ability to fly • Escape & dispersal • Small • Short life spans • Quick adaptations

  11. Insects and People • Competition for food  • Spread diseases  • Plague, typhoid fever, malaria • Consume clothing & carpet  • Crop pollination  • Make commercial products  • Wax, silk, honey • Recycle nutrients  Video

  12. Insect Development • Hatchling must go through several molts to reach adulthood (sexual maturity) • Metamorphosis: major developmental changes from larvae to adult • Two forms: incomplete & complete

  13. Incomplete Metamorphosis • Nymph: immature form of insect that looks like adult • Only the adult can fly and is sexually mature

  14. Complete Metamorphosis • Two stages of development that look drastically different • Pupa: changing from larvae to adult • Cocoon: protective covering of pupa • Chrysalis: butterfly pupa protection

  15. Insect Defense • Passive defenseexamples: • Camouflage • Look like plants • Aggressive defenseexamples: • Venomous stingers • Harmful chemicals • Warning coloration:color pattern to warn of poison

  16. Mimicry • Mullerian mimicry: poisonous species mimics the coloration of another poisonous species • Bees & wasps • Batesian mimicry: harmless species mimics the coloration of a poisonous species • Monarch & viceroy butterflies

  17. Grasshoppers Subphylum Hexapoda

  18. External Structures: • Head = mouthparts, antennae, simple & compound eyes • Thorax = 3 parts: • Prothorax= 1st pair walking legs • Mesothorax = 2nd pair walking legs & forewings (protective) • Metathorax = 3rd pair legs (jumping) & hindwings (flying)

  19. Abdomen = upper & lower plates connected by flexible exoskeleton • Covered by waxy cuticle (prevents desiccation)

  20. Feeding • Chewing mouthparts (feed on plants) • Labrum: functions like upper lip • Labium: functions like lower lip • Mandible: tears food • Maxilla: helps hold & cut food Video

  21. Digestive Tract • Mouth saliva (from salivary glands)  esophagus  crop (storage)  gizzard  midgut/stomach (bathed in enzymes from gastic ceca)  nutrients absorbed in hindgut/intestine  anus

  22. Circulation, Respiration, & Excretion • Circulatory system: • Open • Aorta (large, dorsal vessel) • Heart (pumping organ) • Respiratory system: • Tracheae (site of air diffusion inside body) • Spiracles(openings to allow air in/out) • Excretory system: • Malpighian tubules: return most water back to hemolymph, rest leaves body via feces

  23. Neural Control • CNS = brain, ventral nerve cord, & ganglia at each segment • Antennae– touch & smell • 3 simple eyes– intensity of light • 2 compound eyes– sight • Tympanum – sound & communication • Sensory hairs- touch

  24. Reproduction • Separate sexes (male & female) • Sexual Reproduction: • male deposits sperm into female seminal receptacles • Eggs released from ovaries • Internal fertilization • Ovipositor: digs a hole in soil to lay eggs

  25. Insect Behavior Section 37.2

  26. Communication • Chemical communicationviapheromones • Chemical released that affects behavior or development of other members of same species • Uses of pheromones: • Attract mates • Identify hives • Food trails video

  27. Communication Con’t… • Sound communicationvia chirping, buzzing, etc. (crickets, mosquitoes) • Attract females • Protect territories • Sight communication via flashes of light (fireflies) • Find mates

  28. Behavior in Honeybees • Social insects: insects that live in colonies with division of labor • Innate behaviors: genetically determined • Not taught or learned • Three types of honeybees: • Worker • Drone • Queen

  29. Worker Bees • Sterile females • First adult week: feed honey & pollen to queen, drones, & larvae • Royal jelly • Next two weeks: secrete wax (build & repair honeycomb), remove wastes, guard hive, circulate air in hive

  30. Continued… • Last weeks of life: collect nectar & pollen • Adaptations: • Barbed stingers for protection of hive • Mouthparts for lapping nectar • Legs with pollen packers, baskets, & pollen combs

  31. Drones • Males developed from unfertilized eggs • Parthenogenesis • Can travel from hive to hive • Sole function: deliver sperm to queen • succeed in mating = death • penis and associated abdominal tissues are ripped from the body at intercourse

  32. Queen Bee • Continuous diet of royal jelly as larvae = queen bee • Secretes pheromone “queen factor” that prevents other females developing into queens • Sole role: reproduction • Mates only once • Sperm remains inside her for 5+ years • Lays millions of eggs per year! Video

  33. The Dances of the Bees • Dancing performed by scout worker bees • Round dance: told workers that food was nearby but not exact location • Waggle dance: told workers that food was far away and told location Round Waggle

  34. Altruistic Behavior • Definition: aiding other individuals at one’s own risk or expense • Kin selection: increasing the propagation of one’s own genes by helping closely related individuals reproduce • Example: worker bee stinging = death Video

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