eduKate Learning Manual — Diversity

Did You Know Most Animal Species Are Insects?

When people imagine “animals”, they often picture mammals first.

Dogs. Cats. Elephants. Whales. Tigers.

But if we look at animal diversity by species, insects dominate.

Smithsonian teaching material puts it in a wonderfully jarring way: roughly four out of every five animal species are insects.

And they are built very differently from us.

We carry our main skeleton inside our bodies.

An insect wears its supportive skeleton on the outside.

So if insects are everywhere, enormously diverse and built on such a different body plan, what makes all of them insects?

Teaching goal: By the end of this manual, a learner should be able to recognise insects from their shared body plan — six legs, three main body regions, one pair of antennae and an exoskeleton — distinguish insects from spiders and other arthropods, and explain how enormous diversity can grow from one underlying structural pattern.

1. The Singapore Primary Science Anchor

Insects are one of the broad animal groups used in the Singapore Primary Science Diversity theme.

The most useful identifying characteristics are:

• six legs;
• three main body regions: head, thorax and abdomen;
• one pair of antennae;
• an external skeleton, called an exoskeleton;
• jointed legs because insects are arthropods.

Many adult insects also have wings, but wings are not required for every insect.

2. Three Main Body Regions

An insect body is organised into three main regions.

Head

The head carries important sense organs and feeding structures.

• eyes;
• antennae;
• mouthparts adapted to the insect’s diet.

Thorax

The thorax is the movement centre.

All six legs attach to the thorax. Wings, when present, also attach here.

Abdomen

The abdomen contains many of the organs involved in digestion, reproduction and other internal functions.

This three-part plan remains recognisable whether the insect is a beetle, butterfly, ant, grasshopper or dragonfly.

3. Six Legs: The Fastest Primary Test

Adult insects have three pairs of legs, making six legs in total.

This is one of the most useful quick classification clues.

A spider has eight legs.

A centipede has many more.

A crab has a different arthropod body plan.

All are arthropods.

Only one is an insect.

4. The Skeleton Is on the Outside

Humans and other vertebrates have an internal skeleton.

Insects have a hard outer body covering called an exoskeleton.

It supports and protects the body while giving the muscles something to pull against for movement.

The material contains chitin, a strong biological material also found in the outer coverings of other arthropods.

But an outside skeleton creates a problem.

How do you grow when your armour does not stretch enough?

You take it off.

5. The Strange Problem of Growing Out of Your Own Body Armour

As many insects grow, they form a new exoskeleton beneath the old one and shed the old outer covering in a process called moulting.

For a period after moulting, the new exoskeleton is softer before it hardens.

If you have ever found the empty brown shell of a cicada clinging to a tree, you may have been looking at an abandoned exoskeleton.

That empty shell is evidence that growth happened differently from the way your own bones grow inside you.

6. Antennae Are Not Decoration

Insects have one pair of antennae.

Antennae are important sensory organs. Depending on the species, they can detect:

• chemicals and smells;
• touch;
• air movement;
• vibrations;
• signals from other insects.

Antennae help insects navigate a world in which chemical and vibration information may matter as much as vision.

7. Wings: Common, Useful, but Not Universal

Many adult insects have one or two pairs of wings.

But some insects are wingless, and some species have winged and wingless forms.

So “has wings” is weaker than “has six legs and the insect body plan”.

The recurring classification lesson appears again:

Do not choose the most dramatic characteristic. Choose the most reliable one.

8. Why a Spider Is Not an Insect

Characteristic	Insect	Spider
Legs	6	8
Main body regions	3: head, thorax, abdomen	2 main regions
Antennae	1 pair	None
Exoskeleton	Yes	Yes
Arthropod	Yes	Yes

The spider and insect share the larger arthropod plan, but they belong to different groups.

This is a useful reminder that classification can be nested: two organisms can share one larger group while differing at a more specific level.

9. The Human Story: Maria Sibylla Merian Looked Carefully

In seventeenth-century Europe, many people still accepted versions of the old idea that insects could simply arise from mud, waste or decaying matter.

Maria Sibylla Merian, an artist and naturalist, did something more useful.

She watched.

From a young age she reared caterpillars and other insects, recording their life cycles and the plants they depended on. Her detailed observations connected caterpillars, pupae and adult butterflies and moths as different stages of one life.

Later she travelled to Suriname and documented insects and plants with extraordinary care.

The heroic part is not that she already knew the answer.

It is that she cared enough to observe the ordinary thing for long enough that the ordinary thing became evidence.

Sometimes discovery begins by refusing to look away too early.

10. The Diversity Shock Comes Home

Beetles, butterflies, ants, bees, dragonflies, grasshoppers, termites, mosquitoes and stick insects can look almost unrelated.

Yet beneath that diversity sits the same basic insect plan:

• six legs;
• head, thorax and abdomen;
• one pair of antennae;
• an exoskeleton;
• jointed appendages.

That is why classification is powerful.

It lets us see unity inside overwhelming variety.

11. Common Misconceptions — and Repairs

• “Anything small and creepy-crawly is an insect.” Spiders, centipedes and many other arthropods are not insects.
• “Insects have eight legs.” Adult insects have six legs.
• “All insects have wings.” Wings are common but not universal.
• “The shell is just skin.” The exoskeleton is a major structural and protective framework.
• “A caterpillar is not an insect because it does not look like a butterfly.” It is the larval stage of an insect life cycle.
• “Most animals are mammals because mammals are the animals we notice.” In species diversity, insects vastly outnumber mammals.

12. Teach It: Build an Insect from the Body Plan

Ask the learner to draw a completely imaginary insect.

It can be purple. Transparent. Enormous. Tiny. It can have strange wings or no wings.

But it must obey the core insect plan.

1. Three main body regions.
2. Six legs attached to the thorax.
3. One pair of antennae.
4. An exoskeleton.

Then ask: How strange can the animal become before it stops being an insect?

That turns memorisation into constraint-based reasoning.

13. Guided Practice

1. An animal has eight legs, no antennae and two main body regions. Is it an insect?
2. An animal has six legs, three main body regions and no wings. Could it still be an insect?
3. Why must an insect moult as it grows?
4. What is the advantage of using six legs rather than “has wings” as an identification clue?

14. Independent Challenge: Find the Insect

Three mystery animals:

• A: eight legs, no antennae, exoskeleton.
• B: six legs, head/thorax/abdomen, one pair of antennae, no wings.
• C: many body segments, many legs, one pair of antennae.

Which is the insect?

Explain using at least three characteristics.

15. How an Adult Should Teach This

• Start with the diversity shock: most animal species are insects.
• Use a spider immediately as the high-value counterexample.
• Let the child physically count six legs on photographs or models.
• Show a shed cicada shell if available safely, or use a photograph, to make exoskeleton moulting visible.
• Tell Merian’s story as a story about careful observation, not as a biography quiz.
• Keep bringing every strange insect back to the shared body plan.

16. What Mastery Looks Like

• Beginning: identifies familiar insects by appearance.
• Developing: counts six legs and names the three body regions.
• Secure: uses antennae, exoskeleton and body plan to distinguish insects from spiders and other arthropods.
• Strong: understands why wing presence is not a universal criterion.
• Advanced for Primary: sees how one underlying body plan can produce extraordinary evolutionary diversity.

17. Singapore Curriculum Boundary

The Primary requirement is to recognise insects as a broad animal group using common observable characteristics. Arthropod taxonomy, chitin chemistry, deep evolutionary history and Maria Sibylla Merian’s scientific legacy are enrichment. They should deepen wonder and reasoning without becoming extra examination burden.

18. Continue the Diversity Sequence

• Previous: Recognising Fish and Their Characteristics
• Next: Recognising Flowering and Non-Flowering Plants
• Later: Understanding Why Classification Needs Clear Criteria

19. Trusted References

• Singapore Ministry of Education — Primary Science Teaching & Learning Syllabus
• Smithsonian National Museum of Natural History — What Is an Insect?
• Smithsonian National Museum of Natural History — Internal and External Skeletons
• Natural History Museum — Maria Sibylla Merian: Metamorphosis Unmasked by Art and Science

eduKate Learning Manual principle: When the world is too diverse to hold in your head, find the structure that lets you see the pattern without losing the wonder.