My favourite Halloween story is a tale of real-life zombies.

I'm not talking corpses with a hunger for brains. This story is about something much smaller.

It's about ants, and a fascinating fungus called Ophiocordyceps unilateralis.

In rainforests in Thailand and Brazil a species of ants, known as Camponotus leonardi (or carpenter ants), are quietly going about their business, doing whatever it is ants do. That is, until they encounter Ophiocordyceps unilateralis. O. unilateralis is a parasitic fungus that infects ants. And when it does, it turns them into zombies.

Carpenter ants live high in the tree-tops, coming down to forage for food, then returning to their nests.

But once infected with the fungus, their behaviour totally changes.

They climb down from the trees, to the forest floor, where they find a suitable leaf, climb underneath it, and bite down to anchor themselves in place.

And then things start to get a bit creepy.

With the host ant anchored to a leaf, still alive, the fungus continues to grow. It weaves its way through the ants' body, through the abdomen and thorax, down the legs, and of course into its head.

Eventually, the fungus erupts from the ants' head, by way of a giant stalk, which then releases fungal spores into the air. These spores fall to the forest floor, ready to infect the next hapless ant that wanders by.

The whole process, from infection to the moment a giant spike erupts from the ants head, takes about 10 days.

That must be a pretty horrific 10 days for the ant, as it is slowly consumed from the inside.

Scientists have been studying this zombie fungus to try and figure out how it can control the behaviour of ants.

At first, it was thought that the fungus must attack and take over the ants' brain.

However, more recently it was discovered that the brain is actually the last part of the ant to be taken over by the fungal growth. Instead the fungus takes over the ants' muscles.

It then uses the ant like a puppet, controlling the movement of the limbs and mouth, steering the ant towards the perfect place for the fungus to reproduce.

So now you all know, zombies are indeed real. Happy Halloween, everyone.

Dr Mary McMillan is a lecturer at the School of Science and Technology, University of New England