1. 蚂蚁 (mǎ yǐ): This is the most common way to write "ant" in Chinese. It is the general term for ants.
2. 蚁 (yǐ): This is a more formal and literary way to write "ant". It is often used in poems and classical texts.
So, depending on the situation, you can use either "蚂蚁" or "蚁" to refer to an ant.