There are more insects on Earth than all other kinds of creatures combined – over 900,000 known species. They are animals in the big group (or Phylum) Arthropoda, which includes crabs, spiders, scorpions and centipedes. Their group (or Class) is called Insecta has many smaller groups (Orders) that break insects down into like insects, like: beetles (Coleoptera), butterflies and moths (Lepidoptera) and grasshoppers (Orthoptera). for a list of insect orders: LINK
Classification of Insects:
Orders: Orthoptera (Grasshoppers and Kaydids)
The study of insects is called entomology.
Insect Pests: Insects can hurt people by damaging food crops and forest trees, spreading diseases like malaria and yellow fever, or just biting and stinging painfully. Examples of insect pests are mosquitoes, caterpillars and fire ants.
Insect Helpers: Insects can also help people by pollinating food crops, making products like honey, supplying animals with food (like song birds, turtles, frogs and bats) and ridding us of other pests like aphids and such. Examples of helpful or beneficial insects are honey bees, praying mantis, and predatory ladybugs.
Looking at Insects: It is fun to collect insects that you find (that are already dead) and study them. Or just see insects outside and watch what they do. To understand insects and make watching them more interesting, there are some things you should know about them.
What Makes a Bug an Insect?
Creatures that are NOT Insects: Some things may be "bugs," but are not true insects. These include spiders, millipedes and centipedes – who are in a bigger group (called a Phylum) with insects called Arthropoda. Other animal groups in Arthropoda are crabs, lobsters, scorpions, and barnacles.
Look for the insect traits you have learned to decide whether or not a bug is really an insect:
Other Important Insect Traits
A good sample insect is the grasshopper. It has all the traits of a typical insect plus some other interesting features.
Other Insects, like butterflies and moths, go though "Complete Metamorphosis” where they go through a complete change from birth to adulthood.
One purpose of this change allows the insect to use several food sources. Early on as a caterpillar, it can eat leaves. Then by the time the adult butterfly emerges, the plants have flowered and they can collect nectar. They can also survive the winter in their pupal phase and try again next summer, though Monarch butterflies will actually migrate, flying all the way to Mexico for the winter months.