Go to any online forum related to gardening and you will find discussions about ant-problem! 
Ant as problem?
What a fall of society! From a land of Kolam to the land of ant-killers?
Ant is not an problem. Problem is with the modern world view which consider everything useless!
In dharmic society, feeding ants before having daily meal is one of the daily mandatory duties. गृहिणी starts her day by making beautiful designs out of rice flour on the ground outside home.
Beautiful Kolam
The rice flour may be used in powder or mixed with water, but the message is clear: even the smallest forms of the creation must be fed. Just one daily ritual – so many purposes solved!! Think about it! I will discuss other benefits later. This post is for ants!
There is a story of ants and Indra. Climate change.
Listen the story here:

During the course of the boy’s talk, a long procession of Ants enters the palace and catches his attention. On seeing the procession of the Ants, the boy laughs loudly. Astonished and equally humbled, Indra asks the boy the reason for his amusement. To Indra’s horror, the boy reveals that the ants were once Indras in their previous lifetimes! For all his celestial splendor, Indra comes to see his own insignificance in the creation when he sees the ants.
When you are consumed by the pride, you go down. Thus onus of responsibility falls on the higher life form to realize and respect the lower life forms. No life form should be killed as we all are interrelated!

Ants and Agriculture

Research undertaken by scientists in China reveals that ants are hardworking and beneficial insects. In the activities of their daily lives, ants help increase air, water flow, and organic matter in soil. The work done by ants even forms a type of mulch that helps hold water in the soil.

Ants are busy insects. They dwell in the soil, and build their homes by burrowing tiny holes, channels, and chambers. Soil scientists refer to these as macropores. Where do ants place the soil they are digging out? On the soil surface. The tiny clumps we see as an ant hill are what researchers call aggregate mulches.

In addition to creating the aggregate mulches, ants help the soil environment by “bringing down food sources from outside,” says soil scientist Tongchuan Li. “Types of food include the bodies of insects, leaves, sugar water, and the ‘honeydew’ of aphids. The big diameter of the nest channels (4.1-6.6mm) and the chambers also can improve the transport of air with frequent ant activities.”

Li and researchers at Northwest A&F University, Yangling, China, found that ant-made aggregate mulches could help retain water in agricultural fields. In other words, these aggregates can act like any other mulch, preserving moisture in the soil, under certain conditions. “Minimal attention has been paid to the effects of ant activities on soil [water] evaporation thus far,” says Li. “Ants represent half of the global insect biomass,” and these mulches could be playing an important role in soil moisture, soil health, and agricultural field efficiency.

Spiritually or otherwise, ants play significant role of eco-system. Don’t foolishly kill them!