clipped from: www.physorg.com   
Army ants form living pothole plugs to speed up delivery
Certain army ants in the rainforests of Central and South America conduct spectacular predatory raids containing up to 200,000 foraging ants. Remarkably, some ants use their bodies to plug potholes in the trail leading back to the nest, making a flatter surface so that prey can be delivered to the developing young at maximum speed.

The raid always remains connected to the nest by a trail of forager traffic, along which prey-laden foragers run back to run back to the nest. This trail can be extremely uneven and full of ‘pot holes’ as it passes over leaves and branches on the forest floor.

Their experiments showed that individuals size-match to the hole they plug and cooperate to plug larger holes. "We did this by getting the ants to literally ‘walk the plank’,