This is the terror of the forests in tropical America.

The army ants (Eciton) make spectacular predatory raids involving up to 200,000 individuals, and everything that is encountered by the killer swarm of ants is dismembered and brought to their nest, from others insects to lizards and mice.

People too can be killed if found sleeping, especially if the ants enter the respiratory paths.

An amazing behavior found in these ants is that some individuals use their bodies to plug potholes in the trail that goes back to the nest, flattening the surface so that prey can be furnished to the developing young in time.

The raid is always linked to the nest by a trail of forager traffic, with prey-laden foraging individuals rushing back to the nest. The path can be very uneven, with a lot of 'pot holes' as it can cross over leaves and branches on the forest ground.

The research made by the team at the University of Bristol revealed how these living 'plugs' increase the overall speed of the traffic and with that the prey quantity that reaches the nest. "I think every road user who has ever inwardly cursed as their vehicle bounced across a pothole - jarring every bone in their body - will identify with this story. When it comes to rapid road repairs, the ants have their own do-it-yourself highways agency", said coauthor Professor Nigel Franks.

"When the traffic has passed, the down-trodden ants climb out of the potholes and follow their nest mates home. Broadly, our research demonstrates that a simple but highly specialized behavior performed by a minority of ant workers can improve the performance of the majority, resulting in a clear benefit for the society as a whole." added Dr Scott Powell.

The ants were found to size-match the hole they plug and cooperate to adjust to larger holes. "We did this by getting the ants to literally 'walk the plank'. We inserted planks drilled with different sizes of hole into the army ants' trails to see how well different sizes of ant matched different sizes of pot hole. Indeed, they fit beautifully", explained Franks.

Counts showed that plugging behavior induces a significant rise in daily prey intake, more than the pothole pluggers would compensate by carrying prey themselves. In other words, an extreme specialization by a minority can improve significantly the overall performance of the colony.