It should be an army ant.

应该用一只行军蚁。

For example, take the army ant, of which around 130 species have been identified in the Americas alone.

用军蚁来作个例子，光光在美国，已被确认了的军蚁种类就有约莫130种。

Any of various dull-colored south american birds that feeding on ants some following army ant swarms.

南美洲各种以蚂蚁为食的深色鸟类，有一些跟着蚂蚁群。

The acacia and its ant army are a textbook example of mutualism between species.

洋槐树和它的蚂蚁亲卫队是物种之间互利共生关系的经典范例。