Insects are the largest group of animals on Earth, with about 1 million known species. Scientists estimate there could be 2 million to 30 million insect species in total. They are found in nearly every environment worldwide, including deserts, mountains, caves, and freshwater.
What Makes an Insect an Insect?
Insects are distinguished by an exoskeleton, three main body parts, six legs, and antennae. The head contains the insect’s eyes, mouthparts, and antennae, used for sensing their surroundings. Insects can have both simple eyes, which sense light, and compound eyes, made of many tiny lenses that give them a wide view.
The thorax is the middle section where its legs are attached. Most adult insects also have one or two pairs of wings connected to their thorax, though some do not have wings. Legs are adapted for various movements, like running, jumping, swimming, or digging.
The abdomen is the rear section, holding internal organs for digestion, waste removal, and reproduction. Unlike humans, insects do not have bones; instead, they have a hard outer covering called an exoskeleton. This exoskeleton is made of chitin and protects it from harm and drying out.
Where Insects Live and What They Eat
Insects live in nearly every environment on Earth. They are found in deserts, mountain streams, and even saltwater, though most prefer land. Forests, gardens, and our homes are common places to find them. Some insects, like young dragonflies, start their lives in water before moving to the air as adults.
Insects have a wide variety of diets, eating almost anything. Many are plant-eaters, consuming leaves, roots, seeds, nectar, or wood. For example, caterpillars and grasshoppers eat leaves, while butterflies and bees drink nectar from flowers using straw-like mouthparts.
Other insects are predators, hunting and eating other small creatures, including other insects. Ladybugs, for instance, eat tiny insects called aphids that can harm plants.
Some insects act as scavengers, feeding on dead animals and fallen trees, which helps recycle nutrients. Certain insects, like fleas and lice, are parasites; they live on or inside other animals and get food, such as blood, from them. Mosquitoes feed on blood from animals, and some even pollinate flowers. Their diverse diets are reflected in different mouthparts, designed for chewing, sucking, or sponging liquids.
Insect Life Cycles and Amazing Tricks
Many insects go through significant changes as they grow from an egg to an adult, a process called metamorphosis. There are two main types: complete and incomplete.
Complete metamorphosis involves four stages: egg, larva, pupa, and adult. A butterfly is a good example; it starts as an egg, hatches into a worm-like larva (a caterpillar), then becomes a pupa (chrysalis), and finally emerges as a winged adult butterfly. Inside the pupa, the insect’s body completely changes, developing features like wings and legs. Bees, moths, and beetles also undergo complete metamorphosis.
In incomplete metamorphosis, insects go through three stages: egg, nymph, and adult. A nymph looks like a tiny version of the adult but usually without wings. Grasshoppers are an example; they hatch from eggs as small nymphs that resemble adults and gradually grow larger, developing wings. As nymphs grow, they molt their exoskeletons several times for a new, larger one.
Insects also have various ways to survive and protect themselves. Some use camouflage, blending in with their surroundings to avoid predators. Many moths, for example, have colors similar to tree bark. Other insects use mimicry, looking like more dangerous animals to scare away threats. Some have hard body armor, like beetles, while others can bite, sting, or produce poisons or sprays to defend themselves.
Why Insects Are Important
Insects play many important roles that keep our planet healthy. One primary role is pollination. Insects like bees, butterflies, and some beetles help flowering plants grow by moving pollen from one flower to another, which allows plants to make fruits and seeds. Without pollinators, many of the foods we eat, like fruits and vegetables, would not be able to grow.
Insects also act as natural recyclers and decomposers. Beetles, ants, and flies help break down dead plants and animals, returning important nutrients to the soil. This process helps create rich topsoil, important for plant growth. Burrowing insects like ants also dig tunnels that help aerate the soil, allowing water to reach plant roots.
Insects are a food source for many other animals. Birds, bats, fish, reptiles, and some mammals rely on insects for their meals. Mosquitoes also provide food for many animals.