What will ants not cross?

Ants will not cross or will avoid crossing several barriers that disrupt their pheromone trails, irritate them, or present physical obstacles, though no barrier is 100 percent effective against all species and persistent ants will often find a way around if food is attractive enough. Common household substances that ants are said to not cross include chalk lines because calcium carbonate is said to disrupt trails, though studies show limited effectiveness, cinnamon powder which irritates them and can block trails temporarily, black pepper and cayenne pepper which irritate, baby powder or talc which clogs their breathing pores, diatomaceous earth which dehydrates insects when they walk through it, coffee grounds which some ants avoid, and white vinegar or lemon juice solutions which erase pheromone trails and have strong smells they dislike. Physical barriers ants will not cross or have difficulty crossing include sticky barriers like petroleum jelly or Tanglefoot applied around table legs, double-sided tape, and water moats, which is why some people place pet food bowls in shallow water to prevent ants from reaching them, as ants cannot swim and avoid water. Ants also avoid crossing very hot surfaces and strong chemical repellents. However, odorous house ants and carpenter ants are persistent and will often cross these barriers if the trail is not completely continuous or if they find a gap, so the most effective way to stop ants is not just barriers but integrated pest management including sanitation, sealing entry points with caulk, and using gel baits that workers carry back to kill the colony, rather than relying solely on lines they will not cross.