Army ants, known for their aggressive foraging techniques, will go to long lengths to get what they want. The name army ant or legionary ant are named for their foraging groups, known as "raids," in which huge numbers of ants forage simultaneously over a certain area. The army ants do not build permanent nests rather the ant colony moves almost continually over the time it exists. Amazing pictures show how millions of army ants work together to invade a hornet nest. As the invasion takes place, the weight of the ants walking upside down causes the ants to loss grip on the soffit yet the shear strength and bond between the ants creates a hanging bridge. When this type of attack happens, most of the hornets escape but the ants do not leave until they’ve completely plundered the honeycomb, carrying hornets, and their pupae, larvae and eggs. For ants, it is more effective to follow the trail over a bridge that goes down and then up than in an inverted upside down walk. Also, it is more likely that upside down the ants can’t carry significant loads.