The name army ant (or legionary ant) is applied to over 200 known species, in different lineages, together characterized primarily by their aggressive predatory foraging groups, known as "raids", in which huge numbers of ants all forage simultaneously over a certain area, attacking prey en masse. They also share the habit of not constructing a permanent nest, unlike most ants, and an army ant colony moves almost incessantly over the time it exists. All species are members of the true ant family Formicidae, but there are several groups that have independently evolved the same basic behavioral and ecological syndrome. This syndrome is often referred to as "legionary behavior", and is an example of convergent evolution.