Ants are useful for clearing out insect pests and aerating the soil. The use of weaver ants in citrus cultivation in southern China is one of the oldest known uses of biological control.^[24] On the other hand, they can become annoyances when they invade homes, yards, gardens and fields. Carpenter ants damage wood by hollowing it out for nesting.

In some parts of the world large ants, especially army ants, are said to be used as sutures by pressing the wound together and applying ants along it. The ant in defensive attitude seizes the edges in its mandibles and locks in place. The body is then cut off and the head and mandibles can remain in place, closing the wound.^[47]

Some species, called killer ants, have a tendency to attack much larger animals during foraging or in defending their nests. Attacks on humans are rare, but the stings and bites can be quite painful and in large enough numbers can be disabling.

The Masai of Africa had an abiding respect for the Siafu ants, voracious predators that consume a large amount of insects and are welcomed for the benefit they bring to farmers, as they will eliminate all pests from a crop and quickly move on.