Lasius is a genus of ants commonly known as "thief ants" or "sugar ants." They are small, typically ranging from 2 to 8 millimeters in length, and are often found in various habitats, including forests, grasslands, and urban areas. These ants are known for their ability to form large colonies, sometimes containing thousands of individuals. Lasius ants are primarily recognized for their foraging behavior, where they search for food sources like sugary substances and proteins. They play a crucial role in the ecosystem by aiding in soil aeration and seed dispersal. Some species within this genus are also known to engage in mutualistic relationships with aphids, protecting them in exchange for honeydew.