You're watching FreeSchool! 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 colors, 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 color, insects make a big difference
for such small creatures. I hope this helped you learn more about insects
today. Goodbye till next time!
