Introduction to the Class Insecta
I. Why Study Insects?
A. Most numerous creatures on Earth
1. 1 human/200 million insects
2. 40 million insects/acre of land
3. 400 pounds of biomass/acre
4. 14 pounds of human biomass/acre
B. Most successful creatures on Earth
1. Insects have entered just about every niche available on
earth except subsurface marine.
a. plant eaters - Destructive, Beneficial,
Pollination, Nectar Feeders
b. they are predators
1. Insects
2. Army Ants - Small birds and animals
3. Aquatic Fly larvae - frogs
c. they are parasites
1. Animals
2. Insects
d. they eat decaying matter - Rove Beetles, Greenhead
larvae
e. blood feeders - Stable flies, greenheads
1. Fleas
2. Lice
3. Mosquitoes
f. animal tear drop feeders
2. Different kinds
a. 900,000 species described
b. 2 to 10 times more undescribed
c. 3/4 of all known animal species
d. 1 out of 5 animals is a beetle
C. Damage
1. Crops
2. Turf/Ornamentals
3. Wood Products
4. Wharehouses
5. Pests
II. What is an insect?
A. Insects are arthropods - Phylum Arthropoda or Jointed
Foot
1. Segmented Bodies
2. Skeleton on the outside of the body
3. A heart on the top of the body cavity
4. A nerve cord on the bottom of the body cavity.
5. May have 1 or more jointed appendages
6. Examples of arthropods
a. spiders
b. crabs
c. shrimp
d. centipedes
e. spiders
B. Other Arthropods
1. Class Crustacea
a. Shrimp, crabs, lobsters, pillbugs
b. Mostly Aquatic
c. Fill marine niches where insects not found
d. Most breathe with gills and have hard outer shell.
e. Body has two regions - cephalothorax and abdomen
f. 2 pair of antennae, legs for swimming
g. Beneficial - exceptions pillbugs,sowbugs and
barnacles.
2. Class Diplopoda
a. Millipedes
b. Cylindrical with 25 to 100 segments
c. Most segment have 2 pairs of legs
d. Beneficial - eat decaying matter
3. Class Chilopoda
a. Centipedes
b. Flattened body with many segments
c. 1 pair of legs per segment
d. Beneficial - eat invertebrates
e. Some can inflict painful bite and inject venom
4. Class Arachnida
a. Major - Spiders, Mites, Ticks, Scorpions
b. Minor - Harvestmen,Whip Scorpions,
Pseudoscorpions
c. Most diverse next to insects
d. 2 body regions - cephalothorax and abdomen
e. No antennae
f. Spiders - Order Araneae
1. unsegmented abdomen connected to
cephalothorax by a thin stalk or pedicel
2. Eight legs
3. Mouthparts for crushing prey and sucking out
juices
4. Silk spinning organs
5. Beneficial
6. Some poisonous
g. Mites and Ticks - Order Acari
1. Pests of man, animals and plants
2. Unsegmented abdomen broadly joined to
cephalothorax
3. Piercing sucking mouthparts
4. Mites
a. feed on plants, animals and organic debris
b. Scabies, plant pests
5. Ticks
a. Feed on animals
b. Transmit disease
5. Class Insecta or Hexapoda
a. 3 body regions - Head, Thorax Abdomen
b. A system air tubes for breathing
c. 3 pairs of jointed legs on the thorax
d. 2 pairs of wings on the thorax
III. Insect History
A. Carboniferous Period - 350 million years ago
1. Colonized land as plant feeders
2. Developed ancient wings
3. Incomplete metamorphosis
4. Developed into predators/parasites
B. Permian Period - 280 million years ago
1. Wings fully developed, folded over abdomen
2. Complete metamorphosis
3. Many common groups seen today - silverfish,
cockroaches, beetles
C. Dominant Life form in terms of numbers
1. Body Structure - exoskeleton, wax layer,
jointed legs (became legs, mouthparts and genitalia)
2. Small Size - protection, food requirements
3. Wings - dispersal,predator avoidance,food
finding
4. Reproductive Output - large number in a short
time
D. Rise of man and agriculture
1. More humans changing the environment
2. Move toward monoculture
3. Movement to community centers
4. Insects become beneficial,pests & health
hazards
E. The plus-minus relationship
1. Plus Side
a. Pollinators
b. Wildlife Food
c. Scavengers
d. Natural Enemies
e. Silk, honey, wax
f. Experimental Animals
2. The Minus Side
a. Crop Damage - direct or indirect
b. Structural damage
c. Annoyance
d. Health problems
IV. What is Entomology
A. Study of insects
1. All relationships dealing with insects
2. Sometimes includes other arthropods - ticks,
spiders, mites
B. Entomologist
1. Person who studies insects or related organisms
2. Studies relationships
3. Studies for criminology
4. Studies as a hobby
5. Studies for pest control
i. What is a pest?
1. An unwanted organism that causes some kind of
damage
2. Types of pests
a. crop pest
b. medical pest
c. aesthetic pest
ii. Pest Status
1. Relative Ranking of a pest in relation to its
damage
2. Dependant on crop, damage and economics
iii. Integrated Pest Management?
The management of pest populations, using all available technologies, below economically damaging levels.
iv. Technologies for Control
1. Chemical
2. Cutural
3. Biological
4. Plant Resistance
a. Classical
b. Genetic Engineering
5. Sterilization
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