Army ants (
Eciton hamatum, shown above) can form living bridges without any oversight from a "lead" ant and with a clear cost-benefit ratio. The ants will create a path up to the point when too many workers are being diverted from collecting food and prey. Bridges will be the length of 10 to 20 ants - only a few centimeters, but swarms form several bridges a day, which save collective energy and maximize foraging time. The ants exhibit a level of collective intelligence that could provide new insights into animal behavior.
Watch the video found here: http://phys.org/news/2015-11-ants-bridges-bodies-video.html
