Yes, insects are animals. Every insect belongs to the animal kingdom (Animalia), the phylum Arthropoda and the class Insecta. They are invertebrates, which means they have no backbone, and they are covered in a hard outer skeleton instead. If you were wondering whether a bee, a ladybird or an ant counts as an animal, the answer is a definite yes.
The idea that "animal" means "furry mammal" is a very common mix-up. In biology, an animal is any member of a huge kingdom of living things that eat other organisms for food, can move at some stage of life and are built from many cells. Insects fit every part of that definition, and there are far more of them than of any other kind of animal.
Are insects animals? The classification ladder
Scientists sort living things into nested groups, a bit like folders inside folders. Each step down the ladder narrows the group. For a honeybee, the ladder looks like this:
- Kingdom: Animalia (animals)
- Phylum: Arthropoda (animals with jointed legs and an exoskeleton)
- Class: Insecta (insects)
- Order: Hymenoptera (bees, wasps and ants)
So an insect is an animal, and it is also an arthropod. The reverse does not work. All insects are animals, but not all animals are insects. A dog, a goldfish, a spider and a snail are all animals, and none of them is an insect.
The word "animal" is also not the same as "mammal" or "vertebrate". Vertebrates are the animals with backbones: fish, amphibians, reptiles, birds and mammals. Insects are on the other side of that split. You can read more about that split in our guide to the differences between vertebrates and invertebrates, or look at the five groups of vertebrates to see which animals insects are not.
What is an insect? The five key features
Many small creatures get called "bugs", but a true insect has a set of features that you can check one by one. Use this list as a quick identification key.
- Three body regions. The body is divided into the head, the thorax (the middle section) and the abdomen (the rear section).
- Six legs. There are three pairs of jointed legs, and all of them are attached to the thorax.
- Two antennae. A pair of feelers on the head used to smell, taste and touch.
- An exoskeleton. A hard, waterproof outer layer that protects the body and stops it drying out.
- Compound eyes. Most insects have eyes made of many tiny lenses, which are good at detecting movement.
Many adult insects also have wings, usually two pairs. Wings are not part of the strict checklist, because some insects, such as fleas, silverfish and worker ants, have none. Legs, body regions and antennae are the most reliable clues.
The infographic above labels these features on a bee. Notice how the three body regions are easy to spot: the head carries the eyes, antennae and mouthparts, the thorax carries the legs and wings, and the abdomen holds the digestive organs and the reproductive organs.
Spot the insect: a photo checklist
Real insects do not look as tidy as a diagram, so it helps to practise on photos. Swipe through these and try to find the head, thorax and abdomen on each one.
Each of these animals looks very different, yet they all follow the same body plan. A dragonfly has four long wings, a beetle folds its front wings into hard cases, and a bee has a hairy thorax for carrying pollen. Evolution has changed the shape of the parts, but the plan of three regions and six legs stays the same.
Why the exoskeleton matters
An exoskeleton is a skeleton on the outside of the body. In insects it is made mostly of a tough, lightweight material called chitin. It does three jobs. It protects soft organs, it gives muscles something firm to pull on, and it is covered by a waxy layer that stops water loss. That last job is a big help for animals that live in air, where water is easily lost.
There is a catch. A hard shell cannot stretch, so a growing insect must shed it in a process called moulting. Just after a moult the new skin is soft and pale, and it hardens within hours. This is why you sometimes see a see-through ghost of an insect clinging to a plant stem.
Next, we will look at the legs, wings and eyes in more detail, and at the inside of an insect, where there is a surprise about how its "blood" and "heart" work.
Six legs, wings and compound eyes
Why six legs?
All the legs of an insect grow from the thorax, and each leg is made of several jointed sections. The shape of the leg depends on the job. A grasshopper has long, powerful back legs for jumping. A honeybee has a "pollen basket" on each back leg. A water beetle has flattened legs that work like oars, and a ladybird has short, strong legs for walking on leaves.
Walking with six legs is also very stable. Many insects move three legs at a time, forming a stable triangle, while the other three swing forward. It is a good example of a structure fitted to its function, which is a favourite idea in biology exams.
Wings: the flying insects
Insects were the first animals to evolve powered flight, and wings are a big reason for their success. Adults of many species have two pairs of wings, but there are plenty of variations:
- Beetles turn their front pair into hard wing cases called elytra, and fly with the back pair.
- Flies use only one pair for flight. The back pair has shrunk into tiny balancing knobs called halteres.
- Bees and wasps have two pairs that hook together in flight.
- Fleas, lice and silverfish have no wings at all.
Flight lets insects escape predators, find mates and reach food or new habitats far away. Dragonflies, for example, hunt other flying insects in mid-air.
Compound eyes and antennae
A compound eye is made up of many tiny units, each with its own lens. Together they build a mosaic image that is not very sharp but is excellent at spotting movement. That is why it is so hard to swat a fly. Many insects also have a few simple eyes that sense the brightness of light.
The two antennae are packed with sense cells. Depending on the species, they detect smells, tastes, air movement, touch and even humidity. Ants "talk" to each other by touching antennae, and many male moths use huge feathery antennae to detect the scent of a female from far away.
Do insects have blood, a heart and lungs?
Insects do have a circulatory system, but it is quite different from ours. Their "blood" is called haemolymph. It is usually pale yellow or greenish, and it does not contain red haemoglobin. Insects have an open circulatory system: a long tube along the back, called the dorsal vessel, pumps the haemolymph forwards, and the fluid then flows freely around the organs inside the body cavity before returning to the tube.
Notice that haemolymph carries little oxygen. Insects breathe in a different way. Air enters through small holes along the sides of the body called spiracles, and then travels along branching air tubes called tracheae directly to the tissues. This works well for small bodies, and it suits small bodies. If you want to compare this with the human system, our notes on animal blood and circulation show closed and open circulatory systems side by side.
Insects are active animals with a nervous system and a brain, and many of them rest or become inactive on a regular cycle. If you are curious about whether that counts as sleep, read do insects sleep?
Are spiders insects? Insect vs spider
No, spiders are not insects. Spiders are animals, and they are arthropods like insects, but they belong to a different class called Arachnida (the arachnids). The two groups look similar from a distance, and both have jointed legs and an exoskeleton. A close look at their body plans shows several clear differences.
| Feature | Insect | Spider |
|---|---|---|
| Class | Insecta | Arachnida |
| Legs | 6 (three pairs) | 8 (four pairs) |
| Body regions | 3: head, thorax, abdomen | 2: cephalothorax and abdomen |
| Antennae | One pair | None |
| Wings | Often present | Never |
| Eyes | Usually compound eyes | Simple eyes, usually several |
The cephalothorax is the head and thorax fused into one section. A spider also has silk glands and spinnerets at the back of its abdomen, which no insect has in the same form. Most spiders also have fangs that inject venom into their prey.
Next we will meet the other arthropods that people often mistake for insects.
Other arthropods, and animals that are not insects at all
Insects are only one class inside the huge phylum Arthropoda. Every arthropod has a segmented body, jointed legs and an exoskeleton, but the groups differ in their number of legs and body regions. Here is a quick guide to the ones that people often mistake for insects.
- Arachnids (spiders, scorpions, ticks and mites): eight legs, two body regions and no antennae.
- Crustaceans (crabs, lobsters, shrimps and woodlice): usually more than eight legs and two pairs of antennae. Woodlice are a good example, because they live in your garden but are crustaceans, not insects.
- Myriapods (centipedes and millipedes): many pairs of legs and a long body made of many segments.
Are scorpions insects?
No. Scorpions are arachnids, so they are relatives of spiders. They have eight legs, two body regions and a pair of pincers, and they have no antennae. The stinger at the tip of the long, jointed tail is part of the abdomen. Bees and wasps also sting, but their stinger is a small structure at the end of a short abdomen, which is a very different design.
Are snails and worms insects?
No, and they are not even arthropods. A snail is a mollusc in the class Gastropoda. It has a soft body, a single muscular foot and usually a shell, and it moves by gliding on a layer of mucus. An earthworm is an annelid, a segmented worm. It has no legs and no hard exoskeleton, and nothing is jointed. Both snails and worms are invertebrates, so like insects they have no backbone, but that is the main thing they share.
This is where the vertebrate and invertebrate split can be confusing. "Invertebrate" is not a single family tree. It simply means "any animal without a backbone", and it includes insects, arachnids, molluscs, worms, jellyfish and many other groups.
Are butterflies and bees insects?
Yes to both. Butterflies and moths belong to the order Lepidoptera, which means "scale wings", because tiny scales cover their wings. Bees, wasps and ants belong to the order Hymenoptera. Both groups have six legs, three body regions, two antennae and an exoskeleton. Ladybirds, which are beetles, are insects too, and so are grasshoppers, dragonflies, flies, mosquitoes and fleas. The moth family is surprisingly varied, and our article on the largest moths in North America shows how big insects can get.
Insect life cycles: complete and incomplete metamorphosis
Most insects hatch from an egg and change shape as they grow. This change is called metamorphosis. Insect eggs are a good example of the variety of ways animals reproduce, and our guide to egg-laying animals puts them in context. There are two main patterns, and they are favourites for exam questions.
Complete metamorphosis: four stages
Butterflies, moths, beetles, bees, ants and flies all go through four distinct stages:
- Egg. The female lays eggs, often on or near the plant the young will eat.
- Larva. The larva (a caterpillar in butterflies and moths, a grub in beetles, a maggot in flies) hatches and spends its time eating and growing.
- Pupa. The larva becomes a pupa, which is called a chrysalis in butterflies. Inside the pupa, the body is rebuilt into the adult form.
- Adult. The adult emerges, can reproduce, and the cycle begins again.
Because the larva and the adult live in very different ways, they usually do not compete for food. A caterpillar chews leaves, while the butterfly sips nectar.
Incomplete metamorphosis: three stages
Grasshoppers, dragonflies, cockroaches and true bugs follow a simpler pattern with three stages: egg, nymph, adult. In many insects, such as grasshoppers, a nymph looks like a small, wingless version of the adult – though dragonfly nymphs live underwater and look quite different. It grows by moulting several times, and at the last moult it gains its wings. There is no pupa stage.
| Feature | Complete metamorphosis | Incomplete metamorphosis |
|---|---|---|
| Stages | Egg, larva, pupa, adult | Egg, nymph, adult |
| Young look like adults? | No | Often (e.g. grasshoppers), but smaller and without wings; dragonfly nymphs look very different |
| Pupa stage? | Yes | No |
| Examples | Butterfly, beetle, bee, fly | Grasshopper, dragonfly, cockroach |
Name the four stages of complete metamorphosis in order. (2 marks)
Egg, larva, pupa, adult. One mark for the first two correct stages and one for the last two in the right order.
Why do a caterpillar and a butterfly not compete for the same food? (2 marks)
The larva has chewing mouthparts and eats leaves, while the adult has a long tongue-like mouthpart for drinking nectar. They therefore use different food sources.
How many species of insect are there?
Insects are the most species-rich group of animals known. About 1 million insect species have been formally described, which is roughly half of all the animal species that have been named. Nobody knows the true total. Older estimates put it at around 5.5 to 6 million, while a 2026 study in the journal Proceedings of the National Academy of Sciences suggested it could be about 20 million. This kind of uncertainty is normal in science, and it simply means a huge number of insects have never been named.
The biggest group is the beetles, with over 350,000 described species. The scientist J. B. S. Haldane is often credited with a joke that God must have "an inordinate fondness for beetles". Whether or not he said it, the numbers support the idea.
Why are insects important?
Insects are small, but their effect on ecosystems is enormous. Three jobs stand out.
Pollination
Bees, hoverflies, butterflies, moths and beetles carry pollen from flower to flower. Researchers estimate that about 87.5% of flowering plant species are pollinated by animals, and that around 35% of global crop production by volume depends on animal pollinators. Insects do most of this work. Our notes on pollination explain the process step by step.
Decomposition and recycling
Dung beetles bury animal droppings, burying beetles clear away dead animals and fly larvae feed on rotting matter. By doing this, insects return nutrients to the soil, where plants can use them again.
Food webs
Insects are food for birds, bats, fish, frogs, lizards and many other animals. Swallows catch flies on the wing, and nestlings of many bird species are fed on caterpillars. Remove the insects and the whole food web wobbles. If food chains are new to you, begin with food chains and food webs and then look at how everything fits together in what an ecosystem is.
Do insects feel pain?
This is an open question in science. Insects have sense organs and a nervous system, and they react to harmful things such as heat or injury. Reacting to danger is called nociception, and it does not prove that an animal feels pain in the way humans do, with an unpleasant emotion attached. Some researchers argue that certain insects may have some form of feeling, and others think their simple brains make it unlikely. Because the evidence is unsettled, the safe and kind approach is to treat insects with care.
The law reflects this uncertainty. The UK's Animal Welfare (Sentience) Act 2022 recognises vertebrates, decapod crustaceans (such as crabs and lobsters) and cephalopods (such as octopuses) as sentient. Insects are not included.
Are insects declining?
You may have heard about an "insect apocalypse". The truth is more complicated, and it is a good example of how scientists weigh up evidence. Two studies are often quoted.
- Hallmann and colleagues (2017, PLOS ONE). Using traps in 63 nature reserves in Germany over 27 years, they found that the total biomass of flying insects fell by about 76% across the season, and by 82% in midsummer. The decline happened in different habitats, and changes in weather and land use did not fully explain it.
- van Klink and colleagues (2020, Science). This was a meta-analysis, which means it combined many studies. It pooled 166 long-term surveys at 1,676 sites. On average, insects living on land declined by about 9% per decade, while freshwater insects increased by about 11% per decade.
Both results matter, but they should be read carefully. The van Klink data came mostly from North America and Europe, and the declines were not the same everywhere. Trends were weaker in protected areas, and they were linked to urban development, which suggests that habitat loss and pollution play a part. Scientists also point out that we have very little long-term data for the tropics, where most insect species live, so the global picture is still uncertain. Other researchers have debated how big the declines are, and which insects are most affected.
What is clear is that insects face real pressures: loss of habitat, pesticides, light pollution and climate change. Our articles on biodiversity in jungle ecosystems and the impact of climate change on food chains show why losing small animals can affect large ones.
How you can help insects
- Leave a patch of garden or school field to grow wild.
- Plant flowers that bloom at different times of year.
- Avoid using pesticides where you can.
- Leave some fallen leaves and dead wood for insects to shelter in.
- Put up a bug hotel or provide a shallow dish of water with stones.
- Take part in a local insect or butterfly count.
Guess the animal: flip cards
Quick quiz
Key points to remember
Frequently asked questions about insects
Are insects animals?
Yes. Insects belong to the animal kingdom (Animalia), the phylum Arthropoda and the class Insecta. They are invertebrates, which means they have no backbone. Bees, ants, butterflies and beetles are all animals, in the same way that dogs, birds and fish are.
Are spiders insects?
No. Spiders are arachnids. They have eight legs, two body regions (the cephalothorax and the abdomen), no antennae and no wings. Insects have six legs, three body regions and a pair of antennae. Both groups are arthropods, so they are related, but they are separate classes.
How many legs do insects have?
Adult insects have six legs, arranged in three pairs. All of the legs are attached to the middle section of the body, the thorax. Some young insects, such as caterpillars, have extra false legs, but these are not part of the adult body plan.
Do all insects have wings?
No. Many adult insects have two pairs of wings, but flies use only one pair, and fleas, lice and silverfish have none at all. Worker ants are also wingless. The wings are useful for identification, but legs and body regions are more reliable clues.
Do insects have hearts and blood?
Insects have a long tube along the back called the dorsal vessel, which works like a heart. It pumps a fluid called haemolymph around the body. Haemolymph is not red and carries little oxygen, because insects breathe through spiracles and air tubes called tracheae.
Are scorpions, snails and worms insects?
No. Scorpions are arachnids, like spiders. Snails are molluscs, and earthworms are annelids. None of them has six legs and three body regions. Woodlice are crustaceans. Like insects, they are invertebrates, but they belong to different groups.
How many insect species are there?
About 1 million insect species have been formally described. Estimates of the true total vary widely, from around 5.5 million in older studies to about 20 million in a 2026 study. Beetles are the largest group, with over 350,000 described species.
What is the difference between complete and incomplete metamorphosis?
In complete metamorphosis, an insect passes through four stages: egg, larva, pupa and adult, as butterflies do. In incomplete metamorphosis, there are three stages: egg, nymph and adult, as in grasshoppers. A nymph looks like a small, wingless adult, and there is no pupa.
Why are insects important?
Insects pollinate flowers, including many food crops. They break down dead plants and animals, which recycles nutrients into the soil. They are also an important food source for birds, bats, fish and frogs. Without insects, many ecosystems and food webs would struggle to survive.
Are insects disappearing?
In some places, yes. A German study found a 76% fall in flying insect biomass over 27 years, and a global review found land insects fell by about 9% per decade, although freshwater insects rose. Most data come from Europe and North America, so scientists are still debating the global picture.
