ENTOMOLOGY 10

Caterpillars of Polyphemus moth feeding on leaves

Insectivorous (Entomophagous) Plants

  1. Charles Darwin's "Insectivorous Plants" (1875)
  2. Occurrence -- about 500 species
    1. Nitrogen-poor soils
    2. Acid bogs
    3. Heavy volcanic clays
  3. Mechanisms to "trap" insects (associated with an attractant)
    1. Sticky exudates (attractive to insects) to entangle them -- fly catcher
    2. Modified structures (spots of color or nectar) to capture them -- pitcher plants
    3. Modified leaves (color and nectar-like substance) to entrap insects -- Venus fly trap
  4. Digestion - glands with enzymatic fluid to digest insects (not exoskeleton)
  5. Absorb nutrients through plant tissues

NO READINGS IN GULLAN AND CRANSTON.

Reference: Evans, H. E. 1984. Insect Biology. Addison-Wesley, Reading, MA.
Insectivorous Plants, pp. 248-249

What Insects Do for a Living: Phytophages (Including plant defenses)

  1. Definitions:
    1. Phytophagous = feeding on living plants (= Herbivores)
    2. Plants are primary producers = Autotrophs that use energy from the sun and chlorophyll to produce biomass.
    3. Insects are consumers = Heterotrophs
      1. Primary consumers (Phytophages)
      2. Secondary or Tertiary (or higher level) consumers
        Predators, Parasitoids, Parasites, Hyperparasitoids
      3. Scavengers on dead organic material (plant &/or animal)
    4. Specificity
      1. Monophagy (silkworm, klamath beetle, elm leaf beetle)
      2. Oligophagy (most herbivores; gypsy moth, spruce budworm)
      3. Polyphagy (grasshoppers, armyworms)
  2. Frequency (Diversity)
    1. Most insects [50%] are herbivores
    2. Most herbivores feed on flowering plants (Angiospermae)
    3. Herbivores are found in most major orders, especially: Orthoptera, Hemiptera, Thysanoptera, Coleoptera, Diptera, Lepidoptera, Hymenoptera
  3. Parts of living plants fed on or in by insects:
    1. Flowers (pollen, nectar, other tissues)
    2. Fruits
    3. Seeds
    4. Leaves (including: extrafloral nectaries; "Food bodies")
    5. Stems & trunks (Cambium, Wood)
    6. Roots
    7. Sap
  4. Types of feeding on/in plant tissues
    1. External feeders (exposed): defoliators, suckers, skeletonizers
    2. External feeders (protected): leaf rollers, case bearers, gall formers (open galls)
    3. Internal feeders: gall formers (closed galls), miners, borers
  5. Plant defenses (Evolutionary arms race) [Coevolution)
    1. Physical: spines, trichomes, tough/thick cuticle, exudates
    2. Chemical: secondary plant compounds (not involved in primary metabolism)
    3. Phenology/Dispersion: escape in time/Space
    4. Tolerance: ability to repair or recover from damage, &/or withstand infestation
    5. Nutritional: not supplying all nutrients insects need for development
    6. Attraction of natural enemies [e.g., extrafloral nectaries,]
    7. Induced resistance
    8. Agricultural plant breeding/genetic engineering (transgenic plants)
    9. Tritrophic interactions [e.g., producer-herbivore-carnivore]

Readings in Gullan, P.J. and Cranston, P. S. (1994). The Insects: An Outline of Entomology:
Read: pp. 248-263 (10-10.2.5); pp. 272-273 (10.4.1); pp. 426-427 (15.6, 15.6.1)

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