Insects have been on Earth for more than 300 million years. Over one million species of insects are known, making them the most abundant group of animals on Earth.
Insects are a part of a large group of creatures called invertebrates. Instead of back bones, invertebrates have an exoskeleton, a hard outer shell to protect their internal organs. All insects have three major body parts: head, thorax, and abdomen. Most insects also have two pairs of wings, except for flies, which only have one pair, attached to their thorax.
Insects are also unique because of their blood, which is called hemolymph, and is very different from human blood. Whereas human blood is red, the blood of insects is light green or clear, for example. Also, human blood travels through veins and arteries, while an insect's blood moves freely throughout its body.
Insects do breathe, but differently than humans do. They breathe through tiny holes, called spiracles, on the outside of their abdomens.
Insects live in many different environments around the world, including in frozen areas at the North and South Poles as well as in hot deserts, rivers, lakes, and large cities.
Even though insects are such a common part of our world and our everyday lives, they're still so unique and interesting to learn about. Next time you see a fly, a mosquito, or even a gnat, stop and take time to observe its interesting body and life!