1. Insect Characteristics
Rainier Jr/Sr High School
Advanced Life Science
Mr. Taylor

2. Insect Characteristics
Insects are the largest single class of organisms with >700,000 named species
This is > ½ of the total named species of organisms (including plants and fungi!)
Insects are the only invertebrates to fly … resulting in a great natural selective advantage.

3. Insect Characteristics
4 main orders of Insects (several minor orders will be ignored)
Diptera: “two-winged” includes flies and mosquitoes
Lepidoptera: “scale-winged” includes butterflies and moths
Hymenoptera: “membrane-winged”: includes bees, wasps, and ants. Many social insects.
Coleoptera: “shield-winged”: beetles. Largest group of insects.

4. Insect Characteristics
Body plan: 3 divisions
Head
1st segment have 2 antennae … sensory
2nd segment has mandibles … obtain food
Next segments have other specialized mouthparts. Insects are extremely specialized in their methods of obtaining food supplies.
Also have compound eyes.

5. Insect Characteristics
Body plan: 3 divisions
Thorax
3 fused segments each have a set of walking legs.
2 of the segments also have wings on most insects.
Wings are made of chitin with supporting veins. Veins are filled with air, not blood or other fluid.

6. Insect Characteristics
Body plan: 3 divisions
Abdomen
9-11 segments
Contain most of digestive and reproductive organs.
No appendages attached to abdomen.

7. Insect Characteristics
Digestive system
Specialized mouthparts for specialized feeding allow for minimal competition.

8. Insect Characteristics
Digestive system
Food passes through
Mouth; food is ground up
Crop: more grinding, addition of digestive enzymes.
Gizzard; mixing of food, enzymes act on food.
Midgut/stomach; most absorption here.
Anus; indigestible wastes are passed out.

9. Insect Characteristics
Excretory system:
Malpighian tubules: eliminate nitrogen wastes as urea: allows for conservation of water.

10. Insect Characteristics
Respiratory System
Most have spiracles and tracheae.

11. Insect Characteristics
Nervous System
Ventral nerve cords with ganglia in each segment.
Brain in anterior segment.
Also have antennae (1 pair): chemo- and touch-receptors. Sensors are extremely sensitive.

12. Insect Characteristics
Life Cycle
Most undergo complete metamorphosis
Adult lays egg
Egg hatches to larva
Larva wraps in chrysalis to become pupa
Pupa emerges as an adult
Most larva feed on different food than adults: a means of minimizing competition.

13. Insect Characteristics
Life Cycle
Some undergo incomplete metamorphosis
Adult lays egg
Egg hatches into a wingless nymph.
Less mature nymph molts to more mature nymph.
Several nymphs later, the adult form appears.

14. Insect Characteristics
Reproduction
Sexual
Internal and external fertilization
Some females have pouches to store sperm, often for long periods of time
Eggs often resistant to heat, cold, dryness. This allows survival of species during long periods of unfavorable conditions (winter, drought, etc)

15. Insect Characteristics
Flight
First animals with wings to appear in fossil record.
This allowed insects to invade and exploit new environments.
This allowed insects to escape predators better
Most have 2 sets of wings, some have only 1 (house flies), a few have no wings (fleas).
Usually only one set of wings used for flight.