Should you kill ants or leave them?

Whether you should kill ants or leave them depends on where they are, what species they are, and whether they pose a problem, as ants play both beneficial and pest roles. Outdoors, you should generally leave ants alone because they are beneficial ecosystem engineers that aerate soil, decompose organic matter, and prey on other pests including termites, caterpillars, and flies, with many species like field ants and pavement ants being harmless outside. In gardens, some ants protect aphids for honeydew, which can be a problem, but overall they help control pests. Indoors, you should kill or control ants that invade kitchens and pantries because odorous house ants, pharaoh ants, and carpenter ants contaminate food, can spread bacteria, and carpenter ants excavate damp wood to build nests causing structural damage over time, with one colony containing thousands of workers. However, indiscriminately squishing a few ants can make the problem worse because when odorous house ants are crushed they release alarm pheromones that attract more ants from the colony, and killing only foragers does not eliminate the queen and nest. The best approach for indoor ants is integrated pest management, which means sanitation by storing food in sealed containers and cleaning crumbs, sealing entry points with caulk, and using targeted gel baits containing fipronil or borax that worker ants carry back to the colony to kill the queen and entire colony within days, rather than just spraying repellents that cause budding. So leave ants alone outdoors, but control them indoors with baits rather than just squishing.