Insects

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Insects

• Chapter 37

2
The Insect World

• Section 37.1

3
Characteristics of Insects

• 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

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Head
Thorax
Abdomen
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Exoskeleton with

• Antennae Examples

• Leg Examples

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Appendage examples
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Two types of mouthparts
Sucking
Chewing
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Entomology

• The study of insects
• other terrestrial arthropods
• Person entomologist
• Classify insects into 25 orders based up
• Mouthparts
• Number of wings
• Type of development

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Classification of Insects

• Subphylum Hexapoda
• Class Insecta
• Common Orders
• Hemiptera
• Homoptera
• Isoptera
• Odonata
• Orthoptera
• Coleoptera
• Diptera
• Hymenoptera
• Lepidoptera

Table on page 743
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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

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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
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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

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Incomplete Metamorphosis

• Nymph immature form of insect that looks like
  adult
• Only the adult can fly and is sexually mature

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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

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Insect Defense

• Passive defense examples
• Camouflage
• Look like plants
• Aggressive defense examples
• Venomous stingers
• Harmful chemicals
• Warning coloration color pattern to warn of
  poison

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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

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Grasshoppers

• Subphylum Hexapoda

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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)

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

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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
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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

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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

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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

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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

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Insect Behavior

• Section 37.2

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Communication

• Chemical communication via pheromones
• Chemical released that affects behavior or
  development of other members of same species
• Uses of pheromones
• Attract mates
• Identify hives
• Food trails

video
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Communication Cont

• Sound communication via chirping, buzzing, etc.
  (crickets, mosquitoes)
• Attract females
• Protect territories
• Sight communication via flashes of light
  (fireflies)
• Find mates

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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

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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

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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

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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

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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
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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
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Altruistic Behavior

• Definition aiding other individuals at ones own
  risk or expense
• Kin selection increasing the propagation of
  ones own genes by helping closely related
  individuals reproduce
• Example worker bee stinging death

Video