Insect Behaviour

Compared to humans, insects have simple nervous systems, and their brains are often smaller than a full stop. But despite this, they have quick reactions, and they often behave in complex ways. All of them know how to search for food, how to escape danger, and how to track down a mate. Some can perform much more impressive feats, such as navigating their way across featureless sand or building elaborate nests. Insect behaviour is controlled mainly by instinct. Instinct is like a computer program that is built into an insect’s brain. It tells an insect what to do, how to do it, and often when to do it as well.

RAPID REACTIONS
The instant a house fly senses danger, it takes emergency action, and launches itself into the air. To do this, it relies on its fast-acting nervous system. The trigger for launch usually comes when its eyes spot movement overhead. Special nerves flash signals from the eyes to the insect’s flight muscles, powering up its wings. At the same time, the fly stows away its tongue and pushes up with its legs. By now, its wings are already buzzing, and in fraction of a second, it is on its way.

BRAINS AND MINI-BRAINS
Like all insects, this cockroach has a brain in its head, and a nerve cord that runs the length of its body. The nerve cord works like a data cable. It collects signals from sense organs and carries them to the brain, and it carries signals from the brain to the muscles. The nerve cord also has a series of ganglia (mini-brains) that control regions of the body, so parts of the body can work on their own. However, the brain is in overall command.

BUILT-IN CLOCKS
These two cockroaches have been caught on camera, feeding after dark. Like all insects, cockroaches cannot tell the time. Instead, their activities are controlled by a chemical clock that ticks away inside their brains. This built-in clock keeps insects in step with the world around them, and it makes sure that they come out at night. If cockroaches are kept in 24-hour daylight, they still come out at night, even though it is not dark.

INSECT REFLEXES
Clinging on to a potato stem, these Colorado beetle larvae look like easy targets for predatory birds. The larvae do not have wings, and their legs are small, so they cannot run away. But if anything touches them, the larvae carry out a simple but effective trick – they let go of the stems with their legs, and drop to the ground. Once the coast is clear, they slowly make their way back up the plant. This kind of behaviour is called a reflex. It can save an insect’s life, but it needs almost no brainpower at all.

INSECT INTELLIGENCE
Holding a pebble in her jaws, this female sand wasp is hammering shut the entrance to her nest. It is a remarkable piece of behaviour, because tool-users are practically unknown in the insect world. Once the nest is sealed up, the wasp puts the pebble back on the ground. Tool-using makes sand wasps look intelligent, but they are not quite as smart at they seem. When a sand wasp picks up a pebble, it is simply following its instincts. Unlike a human or a chimp, it does not understand how tools work.