About Insects INSECTS ARE INVERTEBRATES animals without backbones that have been around for hundreds of millions of years They are the largest and most diverse group of animals found on Earth today WHAT'S THE STORY When people think of prehistoric animals they often picture big creatures like dinosaurs But insects lived back then too In fact the first insects appeared around 480 million years ago That's about 250 million years before the first dino saurs showed up Insects belong to a group of animals called arthropods Arthropods don't have internal skeletons and backbones like people do Instead they have an exoskeleton An exoskeleton is a hard covering on the outside of the animal's body Some exoskeletons are thick and hard others are thin and light Some let water and gases in others keep them out Adaptations in the exoskeleton are one reason that insects have become the most successful animal group on Earth Arthropods have two other notable features that make them easy to identify Their bodies are segmented or divided into parts And their arms and legs are jointed The word arthropod even means jointed leg WHAT IS AN INSECT Insects are just one type of arthropod Others include spiders crabs lobsters cen tipedes and scorpions These organisms share common traits with insects but they're not insects They're distant relatives What makes an insect different Insects have six legs Other arthropods have more An insect's body is divided into three main parts Other arthropods have one or two main body sections Insects usually have wings No other arthropods have wings The three parts of an insect's body are the head thorax and abdomen The head contains mouthparts two antennae and the insect's eyes Legs and wings attach to the thorax Insects move their legs and wings with muscles attached to the exoskeleton on the inside of their bodies The abdomen is at the end of the insect's body It contains the insect's reproductive digestive circulatory and respiratory systems INSECTS FIELD GUIDE
HOW INSECTS USE THEIR BODY PARTS Just like people insects have the senses of sight hearing taste touch and smell But their senses work very differently than ours do Sight Insects can have simple eyes compound eyes both or neither Simple eyes distinguish between dark and light Compound eyes can help insects see a wider range of colors or see in all directions Hearing Many insects can't hear Those that can hear use different body parts to do so Crickets hear with a structure called a tympanum on their front legs Some moths can hear too Taste Most insects taste with their mouthparts or their feet Bees have taste receptors on their antennae Touch Insects have small hairs on their bodies There's a nerve at the base of each hair They can feel objects and changes in air movement around them Smell Insects have receptors on their antennae that detect and gather molecules of odors in the air That's how they smell DARK BROWN LEGS Common Green Darner Wings THREE SMALL EYES BETWEEN COMPOUND EYES GREEN FACE COMPOUND EYES TWO SETS OF CLEAR WINGS WITH BLACK VEINS Cicada Eyes THE COMMON GREEN DARNER RIGHT HAS TWO SETS OF WINGS THE CICADA LEFT HAS TWO LARGE COMPOUND AND THREE SMALL EYES ABOUT INSECTS
