What Makes an Insect an Insect?

To the majority of human beings, insects are a source of disgust, fear, and apprehension. However, insects are creatures that have an important place in our world, with literally millions of spieces of insects in existence. They are a subcategory of arthropods, which are creatures that have bodies divided into segments, and exoskeletons.

There are a number of characteristics that make them easily identifiable and distinguishable from other animals that you might mistake for insects if you don't know any better. One such distinguishable characteristic is that insects have bodies divided into three segments. Those three segments are the head, the thorax, and the abdomen. The head is pretty much what you what expect, while the thorax is like a torso that connects to the head. And the abdomen is attached to the thorax, like the backside of the insect.
Another thing that sets insects apart from different creatures is their six jointed legs. There are three pairs of legs in all, and all of them attach to the thorax. If you see a small creature that looks like an insect but it has legs attached to the abdomen, then it is not an insect. Another typical trait of insects is that they have antennae protruding from their head. It is worth noting that this is typical of insects, but that a small number of insects do not have antennae. Having wings is another characteristic of insects. There are a few spieces of insects that can not fly, but they will have wings at some time during their life cycle. One final characteristic is the insect's hard exoskeleton.

It is fairly straightforward to identify insects based on those characteristics. The trouble comes at stages of the insect's life cycle when it may not display all of those features. As an example, butterflies may exhibit wings and antennae, but caterpillars don't. So it is very helpful to look at both an adult specimen and maturing specimen.

Let's have a look at some animals that are commonly mixed up with insects. As you may know, spiders are not insects but rather arachnids, which we can see by counting their legs. Spiders have eight legs, so right away we know that they can't be insects. Slugs and snails are not insects either, as we can confirm by counting their legs: wait, they don't have any legs! One more example is the centipede. Centipedes are creatures called chilopa, not insects. They don't possess a set number of limbs, instead having a single pair of legs per body segment. And centipedes have a large number of body segments!And centipedes can have very long bodies with many many body segments.