Every insect has six legs, three body parts and, as an adult, usually wings. Past that, they split into about thirty orders, and most people only ever meet a dozen. This is a tour of those dozen: what marks each one out, what it eats, how it grows up, and a species from the Field Guide you can go and find. The A to Z list of names has all 181.
The big five
Five orders hold the great majority of the roughly one million named insects.
Beetles (Coleoptera)
The largest order of animals on Earth. The giveaway is the pair of hard wing cases that meet in a straight line down the back; the flying wings fold underneath. Chewing jaws. Complete metamorphosis: egg, grub-like larva, pupa, adult. Ladybirds, weevils, stag beetles, fireflies and June bugs are all beetles.
Find one: the seven-spot ladybird in any garden, or a European stag beetle on a warm June evening. Browse all beetles.
Butterflies and moths (Lepidoptera)
Wings covered in tiny scales, which is where the colour comes from and why it rubs off on your fingers. A coiled drinking straw for a mouth. Complete metamorphosis with a caterpillar stage. The butterfly-versus-moth split is fuzzy: clubbed antennae and daytime flight usually mean butterfly, feathery antennae and night flight usually mean moth, with exceptions both ways.
Find one: the monarch or cabbage white by day, the luna moth at a porch light. Browse all butterflies and moths.
Bees, wasps and ants (Hymenoptera)
Two pairs of clear wings hooked together (ants only have them briefly, on mating flights), a narrow waist in most, and in females the egg-laying tube that in some species became a sting. Complete metamorphosis. This is the order that invented societies: honey bee hives, wasp nests and ant colonies are all here, alongside thousands of solitary species.
Find one: the western honey bee, the common wasp at a picnic, the black garden ant under a paving slab. Browse all bees, wasps and ants.
Flies (Diptera)
One pair of wings, not two. Where the second pair would be there are two tiny knobs that work as gyroscopes, which is why a fly is so hard to swat. Mouthparts for sponging or piercing. Complete metamorphosis with a maggot stage. Mosquitoes, crane flies, hoverflies and midges are all flies.
Find one: the house fly, the marmalade hoverfly pretending to be a wasp, the common house mosquito at dusk. Browse all flies.
True bugs (Hemiptera)
The only insects an entomologist calls “bugs”. A straw-like beak for piercing and sucking, usually plant sap. Front wings that cross over the back, often half hard and half clear, making an X. Incomplete metamorphosis: the young are wingless miniatures of the adult. Stink bugs, aphids, cicadas, water striders and bed bugs are all true bugs.
Find one: the green stink bug on a bean plant, the dog-day cicada by ear in August, a water strider on any still pond. Browse all true bugs and cicadas.
The familiar smaller orders
Grasshoppers, crickets and katydids (Orthoptera)
Long back legs built for jumping, and the ability to sing by rubbing body parts together. Incomplete metamorphosis. Grasshoppers have short antennae and sing by day; crickets and katydids have long antennae and sing at night.
Find one: the common field grasshopper in any meadow, the house cricket behind a warm wall. Browse all grasshoppers and crickets.
Dragonflies and damselflies (Odonata)
Two pairs of long clear wings, enormous eyes, and a body built for hunting on the wing. The young live underwater for months or years as predatory nymphs. Incomplete metamorphosis, but with such a change of habitat that it looks like a transformation. Dragonflies rest with wings out flat; most damselflies fold them over the back.
Find one: the emperor dragonfly patrolling a pond, the azure damselfly on the reeds beside it. Browse all dragonflies and damselflies.
Mantises (Mantodea) and stick insects (Phasmatodea)
Two orders that are all about waiting. Mantises have a triangular head that swivels, folded front legs lined with spines, and patience. Stick and leaf insects are the masters of looking like a plant. Both grow by incomplete metamorphosis.
Find one: the European mantis in late summer grass, the common walkingstick on an oak. Browse mantids and stick insects.
Cockroaches and termites (Blattodea)
Cockroaches are flattened, fast, and older than the dinosaurs. Termites turned out to be social cockroaches and now share the order. Incomplete metamorphosis.
Find one: the German cockroach if you are unlucky, the eastern subterranean termite on a spring swarm day.
Earwigs (Dermaptera)
Pincers at the back end, used for defence and folding their wings, which are almost never used. Not interested in ears. Incomplete metamorphosis, and unusually for insects the mother guards her eggs.
Find one: the common earwig under a flowerpot.
Lacewings, antlions and their relatives (Neuroptera)
Delicate net-veined wings held like a tent. The larvae are the fierce ones: aphid lions and antlions with sickle jaws. Complete metamorphosis.
Find one: the green lacewing at a lit window in summer.
Mayflies (Ephemeroptera)
The oldest winged insects still around. The young live in streams; the adults have no working mouth and live for a day or two, sometimes an hour.
Find one: the common mayfly over a clean river in May and June.
Three ways to sort an insect fast
- Count the wings. One pair: a fly. Two pairs with hard front covers: a beetle. Two pairs, scaly: a butterfly or moth. Two clear pairs and a waist: a wasp or bee.
- Look at the mouth. A beak means a true bug (or a mosquito, which is a fly with a beak). Jaws mean a beetle, grasshopper, wasp or dragonfly. A coiled straw means a butterfly or moth.
- Look at the young. If the babies look like tiny wingless adults, the order grows by incomplete metamorphosis (true bugs, grasshoppers, dragonflies, mantises, cockroaches, earwigs). If the babies are grubs, caterpillars or maggots, it is complete metamorphosis (beetles, butterflies, bees, flies, lacewings). There is a whole guide to insect life cycles.
Front desk note: beetles alone are about one in four of all named animals. If you find something and cannot place it, “beetle” is the statistically safest guess, and the wing cases meeting in a straight line down the back will confirm it.
And the things that are not insects
Spiders, scorpions, ticks and mites (eight legs), centipedes and millipedes (many legs), woodlice (fourteen legs, crustaceans) and snails and slugs (no legs at all) all get called bugs and none of them are insects. They have their own sets in the Field Guide: spiders and kin and crawlers, and there is a short guide on why spiders are not insects.
Found one and want to know which order it is in? A photo in the identifier gives the species, and every species page says which group it belongs to.
Questions
How many types of insects are there?
Around a million insect species have been described and named, sorted into roughly 30 orders. Five orders hold most of them: beetles, butterflies and moths, bees/wasps/ants, flies, and true bugs. Together those five are well over three quarters of all known insects.
What are the main types of insects?
The big five are beetles (Coleoptera), butterflies and moths (Lepidoptera), bees, wasps and ants (Hymenoptera), flies (Diptera) and true bugs (Hemiptera). Smaller but familiar orders include grasshoppers and crickets, dragonflies, mantises, cockroaches and termites, earwigs, and stick insects.
How do I tell a beetle from a true bug?
Look at the back. A beetle's hard wing cases meet in a straight line down the middle. A true bug's front wings cross over each other and are half leathery, half clear, which makes an X on the back. True bugs also have a straw-like beak for sucking; beetles have chewing jaws.
Are spiders a type of insect?
No. Spiders, scorpions, ticks and mites are arachnids: eight legs, two body parts, no antennae. Insects have six legs, three body parts and antennae. Both are arthropods, which is why they get grouped together in everyday speech.
