Herbivory

• How many insects are herbivorous?

  Nearly half, contributes to 3 of the largest living families of things
• Have insects helped shape the evolution of the plant kingdom?

  Yes, through herbivory
• What do external feeders do?

  Chew, suck, skeletonize
• What do internal feeders do?

  Leaf miners, gall formation, wood boring
• What do insects do to prevent dessication?

  Seek shade, drink water, feed at night, create protective feeding microhabitats
• What are insect nutritional challenges?

  Nitrogen is limiting
• How can insects circumvent a nitrogen deficiency?

  Feed on young plant tissue or seeds

  Mature over a long period of time

  Form galls
• What are insect nutritional challenges?

  Cholesterol is limited
• How can insects obtain cholesterol?

  Feed on young plant tissue

  Mutualist microbes
• What are insect nutritional challenges?

  Low potassium and sodium
• How can insects obtain K+ and Na+?

  Excrete excess K+ or increase Na+ by feeding on urine
• Do insects need animo acids?

  Yes

  They can obtain this by eating a variety and having gut mutualists
• How can insects conserve or get rid of water?

  Modify their malpighian tubules and rectum

  Filter chamber

  Behaviour modification
• Are the absence antifeeding agents more powerful?

  Yes, they are more powerful than the presence of phagostimulants
• What are plant feeding cues?

  Volatiles, trichomes, wax, color, sugar, water, toxin, latex
• What is plant tolerance?

  Plants that survive feeding damage

  Compensate with rapid growth or produce many seeds
• Mechanical antixenosis? (Corn Earworm)

  Development of smooth leafed cotton to combat insect attacks, as opposed to fuzzy cotton varieties

  
• Chemical antixenosis?

  Reduction of cucurbitacins (phagostimulant) to lower attack by beetles

  
• Cabbage aphids?

  Will not feed on red cabbages

  
• Visual antixenosis?

  Production of red colored oats, cabbage, and cotton to combat fly damage

  
• Indirect resistance?

  Some plants can produce wound hormones, terpenoids attract parasitoids
• Antibiosis?

  Chrysanthemums produce pyrethrins that causes paralysis due to the gating of voltage ion channels