Farming ants are master herders

Ever since humans moved from subsistence farming to mass produced agriculture, farmers have employed techniques to improve their yield. But now it seems we were beaten to it by an unlikely farming expert – the ant.

Ants herd aphids to keep their food source close

New research suggests chemicals on ants’ feet tranquilise and subdue colonies of aphids, keeping them close-by as a ready source of food. The study throws new light on the complex relationship between ants and the colonies of aphids whose sugary secretions the ants eat.

Lead researcher Tom Oliver from Imperial college’s Department of Life Sciences said: “We believe that ants could use the tranquillising chemicals in their footprints to maintain a populous ‘farm’ of aphids close their colony, to provide honeydew on tap. Ants have even been known to occasionally eat some of the aphids themselves, so subduing them in this way is obviously a great way to keep renewable honeydew and prey easily available.”

Scientists had previously established that certain types of aphids live in colonies where they are used as a food source by a neighbouring colony of ants. The ants have been known to bite the wings off the aphids in order to stop them from getting away and depriving the ants of one of their staple foods - the sugar-rich sticky honeydew which is excreted by aphids when they eat plants. Chemicals produced in the glands of ants can also sabotage the growth of aphid wings.

This new study - carried out by a team from Imperial College London, Royal Holloway University of London, and the University of Reading - shows, for the first time, that ants’ chemical footprints, known to be used by ants to mark out their territory, also play a key role in manipulating the aphid colony, and keeping it nearby.

However, Oliver points out that the relationship between the ants and the aphids might not be that straightforward: “There are some definite advantages for aphids being ‘farmed’ like this by ants for their honeydew. Ants have been documented attacking and fighting off ladybirds and other predators that have tried to eat their aphids. It’s possible that the aphids are using this chemical footprint as a way of staying within the protection of the ants.”