Ed Golson Outdoor Education

what are insects?

Insects are everywhere! There are more than 20,000 species of insects in Michigan alone. There are many times more types of insects than there are all the other types of animals combined. They may be small, but insects are often called the dominant life-form on the planet.

Insects play a very important role in the environment. They can be both good and bad. Some insects eat valuable crops or spread disease. Other insects are very useful pollinators or eat other pesky insects. Insects are extremely helpful since they eat dead plant and animal material which ensures that we aren't knee deep in dead things all the time.

So, what exactly makes an insect? Insects are small invertebrates-meaning they don't have a back bone. In fact, they don't have any bones at all. Instead, they have a protective covering called an exoskeleton on the outside of their bodies. The exoskeleton supports the insects body like a normal skeleton and makes the insect very durable. The exoskeleton, however, does not grow with the insect. Insects must shed or "molt" its exoskeleton every time it grows.

All insects have three main body segments: a head, thorax, and abdomen. The head is used for eating and processing information- "thinking". The thorax is where the insects' three pairs of legs and wings are attached. The abdomen is used for reproduction.

Other invertebrates like spiders or millipedes have a different number of body segments and legs. They may look like insects, but they aren't.

Insects can go through incomplete/simple or complete metamorphosis. About 88% of insects go through a complete metamorphosis and the following is an example.  A female insect lays eggs and this is the first stage. These eggs are often covered by an egg case which protects the eggs and hold them together.  When they hatch they are in the second stage when they are called larva or nymphs.  It is during the larval form when insects do most of their growing. The larval form of an insects life cycle often looks nothing like the adult form, often having a worm-like shape.

Most insects have a phase before reaching adulthood called a pupa stage.  During this period, the insect does not move or eat and undergoes a complete shape change or metamorphosis . A common example of metamorphosis is when a caterpillar changes into a moth. Often, the insect will form a protective cocoon around itself during this period.  Their bodies develop into an adult shape with wings, legs, internal organs, etc.  This change takes anywhere from 4 days to many months.

The last stage of the insect's life cycle is the adult stage.  Inside the cocoon, the larvae change into adults and after a period of time, the adult breaks out of the cocoon.  During the adult stage, the insect is fully grown and focuses mainly on reproduction.

In a simple/incomplete metamorphosis, the female insects lays eggs.  The next stage is the larval stage.  Here the immature forms, nymphs look very similar to the adult insect in form except for being smaller and lacking fully developed wings.  Most adults and nymphs have the same habits and live in the same environment.  There is no pupal stage.  Examples of insects who have this type of metamorphosis are dragonflies and grasshoppers.

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