1. Insects The largest group of arthropods are the insects.
There are more species of insects than of all other groups combined.
There may be as many as 300 million insects for every person on Earth.

2. Insect Characteristics
Insects are described as having a body that is divided into three parts:
A head
A chest
An abdomen
They also have three pairs of legs attached to the chest part.

3. Insect Structure Insects also have compound and simple eyes.
A simple eye can only detect light and dark.
A compound eye can distinguish colors and detect movement.
Most insects also have wings, normally two pairs of wings.
Insects also use a series of tubes to get oxygen through their exoskeleton and into their body cavity.

4. Growth and Development of Insects: Metamorphosis
Insects grow rapidly and shed their exoskeletons as they get larger.
The growth process of insects is called metamorphosis and involves several stages of development.
There are two types of metamorphosis: complete and incomplete.

5. Complete Metamorphosis
During complete metamorphosis, insects pass through a four stage process.
The first stage produces an egg.
The second stage occurs when the egg hatches into a larva
The third stage occurs as the larva grows into a pupa which are sometimes contained in a cocoon.
The fourth stage is the adult stage

7. Incomplete Metamorphosis
During incomplete metamorphosis, young animals look very much like the adults hatch from eggs.
The young animals however often do not have the organs and wings of the adult stage.
As the young animal grows, it continues molting and getting larger until it reaches the adult size.

8. Insect Behavior Most insects live alone except to reproduce.
Insects signal they are ready to reproduce using a variety of ways including: buzzing, using light, releasing scents, and other behavior.
Social insects, are insects which cannot survive alone and form colonies or hives.
Each individual performs specific tasks for the colony in order for all the animals to survive.

9. Defense Mechanisms of Insects
Insects have many defense mechanisms that enable them to survive.
Wasps and bees use stingers.
Some insects have camouflage to blend with their surroundings.

10. Roles Insects Play in our World
Consumers (almost all caterpillars, beetles
Predators (some wasps, preying mantis, ladybugs)
Provide food for other organisms in food webs (mosquitoes for frogs, flies for spiders, maggots & grubs for bears)
Decomposers/Scavengers (dung beetles, flies)
Pollination (bees, butterflies, moths)
Symbiotic relationships that help other species survive (ants & acacia trees)
Pests on our food crops (cabbage looper/moth)
Biological control of other plant or animal pests (root & flower knapweed weevil, ladybugs)