The world of insects
What makes an animal an insect, how insects grow by moulting and metamorphosis, how many there are, and why they matter. Then catch and sort minibeasts with a pitfall trap.
Read
Insects are arthropods: animals with a hard outer skeleton (an exoskeleton) and jointed legs. All insects have three main body parts (head, thorax and abdomen), six legs, a pair of antennae, and either no wings or two pairs.[1]
The head holds most of the sense organs. Compound eyes are made of many tiny lenses: the more lenses, the sharper the vision. Most insects breathe through small holes along their sides called spiracles.[3]
An exoskeleton cannot grow, so a young insect has to shed it and form a new, bigger one. This is called moulting.[4]
Many insects change shape completely as they grow: egg, larva, pupa, adult (complete metamorphosis), as in butterflies, beetles and bees. Others, like grasshoppers and dragonflies, go egg, nymph, adult (incomplete metamorphosis).[4]
Scientists have described about 900,000 kinds of insects, and there may be millions more. At any moment about 10 quintillion insects are alive.[2][1]
Insects pollinate about 84% of the crops grown in Europe, break down dead material, and are food for many birds, fish and mammals. Some insects also spread diseases.[6]
Try it: Pitfall trap: insect or not?
You need
- A clean plastic cup or yoghurt pot (with a few small holes in the bottom)
- Trowel
- A few dead leaves
- A small flat piece of wood or tile and four stones as a roof
- White tray, spoon, paintbrush, hand lenses
- Recording sheet
Safety
An adult chooses the spot and checks for hazards. Wear gloves when digging, handle animals gently with a spoon or brush, do not leave the trap for more than one night, release every animal, and wash your hands afterwards.
What to do
- Choose flat ground near plants, not at the bottom of a slope.
- Dig a hole and put the pot in so that its rim is exactly level with the soil. Fill the gaps with soil.
- Put a few leaves in the pot so animals can hide, and put the roof on four stones above it.
- Leave the trap overnight and check it early next morning, before it gets warm.
- Tip the animals gently into a white tray. Count the legs of each one with a hand lens.
- Sort them: six legs = insect; eight legs = spider or relative; many legs = woodlouse, centipede or millipede; no legs = slug, snail or worm.
- Record your results, then release the animals in a sheltered spot near the trap and fill in the hole.
Play: Complete or incomplete?
Does this insect grow by complete metamorphosis (with a pupa) or incomplete metamorphosis (with nymphs)?
Your best score is kept only on this device. Nothing is sent anywhere.
Quiz
Other ages: Ages 6–7 · Ages 15–16