There are many reasons why ants are strong. One cause is that they have a very efficient circulatory system. These insects also have potent mandibles or jaws which they use to bite and munch food. Their bodies are also very tough and resilient, meaning they can withstand a lot of damage. Due to the efficient respiratory system that allows them to take in oxygen and get rid of carbon dioxide very quickly, ants can keep working for long periods without fatigue.