LEARNING OBJECTIVES OF SECTION
After completing this section students should be able to:
- Describe the range of plants and plant structures fed upon by insects.
- Describe the different ways that chewing insects may cause plant damage and give examples of some that cause economic damage.
- Explain how sucking insects obtain their food and describe the damage that they cause.
- Explain why sucking insects are more difficult to control that those with chewing mouthparts.
- Describe the unique relationship between plants and insects that results in the formation of insect galls.
- Describe how insects damage plants through their nest building and oviposition activities and give examples of each.
Terms: Direct damage, chewing damage, omnivorous, oligophagous, sucking damage, honey dew, phloem, xylem, leaf miner, tip moth, oviposition damage, carpenter bee, carpenter ant, mole cricket.
- Detrimental Effects of Insects to Plants.
1. External feeders.
a. Chewing insects.
(1) Grasshoppers.
(2) Colorado potato beetles.
(3) Elm leaf beetles.
(4) Gypsy moth.
b. Piercing-sucking insects.
(1) Aphids.
(2) Bugs.
(3) Scale insects.
2. Internal feeders.
a. Mostly chewing insects.
(1) Bark beetles (phloem feeders).
(2) Borers (xylem feeders).
(3) Weevils (fruits and nuts).
(4) Tip moths.
(5) Leaf miners.
(6) Insect galls--abnormal plant growths caused by insects.
3. Underground feeders.
a. Various mouthpart types.
(1) White grubs.
(2) Cicadas.
(3) Mole crickets.
4. Oviposition damage.
a. Cicadas.
b. Sawflies.
5. Nest building activities.
a. Carpenter bees.
b. Leafcutter bees.
c. Carpenter ants.
d. Bag worms.
STUDY QUESTIONS
- What is the primary reason that insects cause damage?
- Many damaging insects have either chewing or sucking mouthparts. Which of these would cause the most visible damage?
- Do you think that insects with piercing-sucking mouthparts or those with chewing mouthparts would be most easy to control?
- What are "scale" insects? Why are they so damaging? Why are they so difficult to control?
- What are insect galls?
- How do you think the relationship between plants and their gall makers evolved?
- Describe the value to insects, and to the plant, of the insect-plant relationship that results in the formation of galls.
- Why do you think that monophagous insects are usually considered more damaging than those with polyphagous feeding habits?
- Give two examples of insects that cause damage through their nest building habits.
- Give two examples of insects that cause damage by their oviposition activities.
Go to Section XIII - Detrimental Effects of Insects to Animals
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