There are over 1 million species of insects, but as you may remember from school, the most basic definition of an insect is an organism with three pairs of legs and three body regions – head, thorax, and abdomen. Entomologists (scientists who study insects) might also add that insects have a pair of antennae and external mouthparts. As you learn more about insects, you will find there are some exceptions to these rules.
The head region is at the front of the insect’s body, and contains the mouthparts, antennae, and eyes.
Insects have mouthparts designed to help them feed on different things. Some insects drink nectar, and have mouthparts modified into a tube called a proboscis to suck up liquid. Other insects havechewing mouthparts and eat leaves or other plant matter. Some insects bite or pinch, and others pierce and suck blood or plant fluids.
The pair of antennae may have obvious segments, or look like a feather. They come in different forms and are a clue to identifying the insect. Antennae are used to perceive sounds, vibrations, and other environmental factors.
Insects can have two types of eyes – compound or simple. Compound eyes are usually large with many lenses, giving the insect a complex image of its surroundings. A simple eye contains just a single lens. Some insects have both kinds of eyes.
The thorax, or middle region of an insect’s body, includes the wings and legs. All six legs are attached to the thorax. The thorax also contains the muscles that control movement.
All insect legs have five parts. Legs can be different shapes, and have different adaptations to help the insect move in its unique habitat. Grasshoppers have legs designed for jumping, while honey bees have legs with special baskets to hold pollen as the bee moves from flower to flower.
Wings also come in different shapes and sizes, and are another important clue to help you identify an insect. Butterflies and moths have wings made of overlapping scales, often in brilliant colors. Some insect wings appear transparent, with just a web of veins to identify their shape. When at rest, insects like beetles and praying mantids keep their wings folded flat against their bodies. Other insects hold their wings vertically, like butterflies and damselflies.
The abdomen is the final region in the insect body, and contains the insect’s vital organs. Insects have digestive organs, including a stomach and intestines, to absorb nutrients from their food and separate waste matter. The sexual organs of the insect are also in the abdomen. Glands that secrete pheremones for marking the insect’s trail or attracting a mate are in this region as well.
The next time you observe a lady beetle or a moth in your yard, stop and take a closer look. See if you can distinguish the head, thorax, and abdomen. Look at the shape of the antennae, and watch how the insect holds its wings. These clues will help you identify a mystery insect, and provide information about how the insect lives, feeds, and moves.