What are insects?

They crawl on leaves. They fly through the air. They even dig in the ground. Insects are practically everywhere! They live on every continent, including Antarctica, although they prefer to live in warm areas. You are probably familiar with some common insects like bees, ants, and butterflies, but insects are the largest group of animals on earth. Nearly a million species have been identified so far, and scientists estimate that there could be millions more just waiting to be discovered. Insects are invertebrates or animals that do not have backbones. In fact, insects do not have any bones at all. Instead, they have a hard outer shell, called an exoskeleton, that gives them their structure. Insects have three main sections of their bodies: the head, the thorax, and the abdomen. They have six legs that are connected to the thorax. Most insects also have wings and antennae.

Although insects breathe air, they do not have lungs. Instead, they have a system of tubes and sacs through which air may pass or be pumped. This system can only carry air so far into the insect’s body, and it is this that limits how large insects can grow. Although there are some very large insects on our planet, they cannot grow as large as other types of animals because after a certain size they could not get enough air into their bodies to support themselves. Another interesting insect characteristic is their eyes! Insects have a special kind of eyes called compound eyes. Compound eyes are made up of hundreds or even thousands of tiny light-sensitive units. Each unit sees only a small part of the insect’s surroundings, but all of them together create a mosaic image – a pattern of light and dark dots. Overall insects do not see as well as humans do and only some can see colours, but their eyes are excellent at detecting motion. Insects are cold-blooded, which means that they cannot control their body temperature. That is why insects usually live in warm places, and why you do not see as many insects during the winter as you do during the summer.

To survive the cold, some insects enter a state called diapause, which is their version of hibernation, and will not become active again until warm weather returns. Insects hatch from eggs, and although some insects hatch as basically small versions of the adults of their species, others go through an incredible change before adulthood. It is called metamorphosis, from a word meaning to transform. The most famous example of metamorphosis in insects is the butterfly. Butterflies begin their lives as caterpillars and spend a few weeks eating and increasing in size. Once they are fully grown, the caterpillars will attach themselves to the underside of a leaf or branch and form a pupa, or chrysalis. The chrysalis hardens into a protective case, and over the next few weeks, the caterpillar inside transforms into a butterfly! When the butterfly is ready to emerge, the chrysalis splits open, but the butterfly cannot fly yet. It hangs upside down, pumping fluid into its wings to make them expand, and slowly opens and closes them to help them dry. Once its wings are ready, the butterfly takes off to find flowers to drink from. Eventually, it will lay eggs of its own, and the cycle starts all over again.

Crawling or flying, alone, or with thousands of friends, insects by the millions are incredibly important to life on earth. Some insects are beneficial to humans, while others are pests, but no matter their shape, size, or colour, insects make a big difference for such small creatures.