We live in a world of insects. Close to one million different species of insects have been identified (compared to only 4,000 or so mammals). That makes insects the most abundant group of creatures on earth. They are found all around the world. One acre of ground may be home to more than a million insects!Insects are part of a large group of animals called invertebrates. Invertebrates do not have a spine (a backbone). Instead they have an exoskeleton -- a hard outer shell that protects them.
All insects have 6 legs. Spiders aren't insects, they're arthropods. You can tell they aren't insects because they have 8 legs.
Most adult insects have three major body parts: the head, thorax and abdomen. The head includes the eyes, antennae, and mouth. The thorax, which separates the head from the abdomen, is where the insects wings and legs are attached. The abdomen is the largest part. It houses the insect's heart, stomach and tubes used for breathing.