1. Insect Anatomy
Do insects have bones?
Insects do not have a backbone like humans and many other animals do.
In fact, insects do not have any bones; they have a hard exoskeleton instead.
‘Exo’ means outside, so that means that the skeleton is on the outside of the
insect’s body instead of on the inside like in our bodies.
Did you know that insects are related to crabs and lobsters, which also have
exoskeletons?
Thinking Scientifically: Animals that have a backbone are called vertebrates – can
you think of any vertebrates?. Any animals that do not have a backbone, like
insects, are called invertebrates.
All insects have three main body parts: a head, thorax, and abdomen. It’s
important to know these parts in order. It helps to think of the thorax as being
sandwiched in between the head (which is at the top just like your own head)
and the abdomen (at the bottom).
Head: An insect has a small head that is a lot like your own head because it
holds the insect’s brain, eyes, and mouth. Insects also have special feelers called
antennae that stick out of the top of their heads. They use their antennae to
smell and feel because they do not have noses and hands like we do.
Thinking Scientifically: You may have heard the word antenna before, but have
you ever heard anyone say antennae (pronounced: an-ten-I)? Did you know that
‘antennae’ is just the plural form of the word ‘antenna’? When we say ‘antenna,’
we are talking about one and when we say ‘antennae,’ we are talking about two
or more, just like when we say ‘shoe’ we are talking one shoe, and when we say
‘shoes’ we are talking about a pair of shoes.
Eyes: Insect eyes are much different from human eyes (called simple eyes).
In fact, insects do not even see things the same way we do! They have two
compound eyes with many different lenses to see out of instead of just one lens
in each eye like we do.
2. Each compound eye can have anywhere from 2 to 30,000 different surfaces that
are very sensitive to light. Compound eyes cannot see very much detail or things
that are far away.
They can see extremely quick movements and things that are close to them,
though. If insects did not have compound eyes, they would have a very difficult
time surviving and finding food!
Have you ever tried to swat a fly? What happened when you got close to it? It
probably flew away the second you got close enough to swat it.
That is because a fly’s compound eyes bulge out of its head so it can see motion
all around its body and see when you are coming closer to it.
Thinking Scientifically: Some insects, like grasshoppers, have compound eyes
and normal eyes (called simple eyes)! With simple eyes, they can see a lot more
detail and see things that are far away.
Thorax: Right below the insect’s
head is a middle section called the
thorax. The thorax of an insect is kind
of like your chest, except insects have
six legs that come out of their thorax!
Insect legs have special joints (sort of
like your knees) and tiny barbs on the
ends instead of toes. Many kinds of
insects have one or two pairs of wings attached to their thorax.
Thinking Scientifically: On insects, wings are always in pairs, just like on
airplanes. Most adult insects have two pairs of wings, but some only have one
pair, and some don’t have any wings at all! Can you think of any insects that do
not have wings? Can you think of some with two pairs and some with only one
pair? (Answers will vary, but here is an example: walking sticks do not have
3. wings, grasshoppers have two pairs, and flies have only one pair of wings. There
are more, can you think of any?)
Abdomen: The part below an insect’s thorax is called the abdomen. It is the
largest part of the insect’s body and contains its stomach, just like your abdomen
does. It also contains the insect’s reproductive system. Insects can reproduce
(have babies) very quickly. Most insects reproduce by laying eggs, like chickens
do, only insect eggs are very tiny and have soft shells.
Thinking Scientifically: To be a true insect, a creature must have a head, thorax,
and abdomen, six legs, two antennae and an exoskeleton. Anything that does
not have at least those characteristics is not an insect. Spiders have eight legs
and two main body parts. Are they insects? No, they sure aren’t! Spiders belong
to a class called arachnids. We do sometimes clump insects, spiders, centipedes,
ticks, and others together and call them ‘bugs.’
Activity #1
Help the pupils write a list of every insect they can think of.
Encourage them to include anything they think is an insect since the goal
of this activity is to develop thoughts.
As your study continues, they will be able to look over their lists again and
cross off any items they included at first that are really not insects (such
as spiders or roly-polys).
How can you tell an insect from a bug or other creepy-crawly creature?
Ask pupils to describe characteristics that insects have in common. Just
get them started with some examples, such as ‘insects have eyes’ or
‘insects do not have tails.’
4. Activity #2
Visual learners will especially benefit from browsing nature magazines,
books, encyclopedias, or the internet for pictures of different insects.
(A Google image search for ‘insects’ will bring up some great photos.)
Have them try to find a picture of each insect on their list or ask them to
find one picture that shows each of the characteristics they mentioned.
How big are the insects you have seen? (Get younger kids to show you
with their hands; older kids might estimate the size of particular insects.)
Some adult insects are less than 1 mm long; that’s really tiny!
On the other hand, some rare stick insects in South America can grow all
the way up to 36 cm (about 14′) long. (Show the contrast between how
big and small these dimensions are on a ruler.)
