91av

Zoologger is our new weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world.

Species name:

Habitat: Europe, generally dry grassy places with flowers. And deep in ant nests

In a grassy field on the edge of a patch of woodland, some ants are escorting a pink caterpillar to their home. Once it has been guided into the depths of their nest, the caterpillar begins feeding the ants with sweet fluids.

It may sound like a touching story of interspecies love, but it ain’t. Over the following year, the caterpillar will eat its way through hundreds of ants, eggs and larvae. So voracious is the intruding caterpillar, there is a good chance that the ant colony will be wiped out.

This deceitful ant-muncher is the caterpillar of the – in adult form, a strikingly beautiful creature with iridescent, spotted wings. But in order to reach adulthood, the caterpillars must infiltrate the ants’ homes, and they have an arsenal of less than beautiful tricks for that purpose.

Back from extinction

The large blue is an example of that rare thing: a conservation success story. It was recently after a led to it being declared extinct in the UK in 1979. It only became possible to restart its British population when conservation biologists realised that for its survival.

The unlucky insect in question is a red ant called , which often inhabits grasslands. They are social ants, living in colonies of around .

So how does a large blue caterpillar sneak its way into the ants’ nests? It doesn’t have to: the worker ants escort it in.

They do this because the waxy coat on the caterpillar’s skin . As far as the ants are concerned, the caterpillar smells like an ant larva and is not a threat.

Royal treatment

That is enough to make the worker ants accept it, but mere acceptance does not satisfy the caterpillar. It will do best if it can convince the worker ants that it is actually a queen ant, deserving the royal treatment.

Like many insects, Myrmica ants communicate using a system of clicking noises. And caterpillars – the large blue – have learned to mimic the sounds the queens make. The worker ants defer to the caterpillar and allow it to plunder their nest.

The caterpillar even pupates within the ants’ nest, which might seem pretty risky. But because it keeps making the clicking noises throughout, the ants generally leave it alone.

Deadly threats

However, the lifestyle of a social parasite is never an easy one, and the caterpillar must face a host of deadly threats.

For one thing, the caterpillar’s chances of survival are much smaller . The caterpillar will also come to grief if it picks too small a nest with not enough food.

But the caterpillars have a trick to get around that too. Some of them develop over allowing them to munch their way to full weight without bringing the ant colony down around their ears.

Video: David Attenborough’s Life in the Undergrowth featured this caterpillar in action –