The genus Lasius is a group of ants commonly found in temperate regions, particularly in North America, Europe, and Asia. These ants are typically small to medium in size and are usually yellow, brown, or black. Lasius ants are known for their underground nests, often constructing large, complex colonies. Many species in this genus are involved in mutualistic relationships with aphids, tending them for honeydew in exchange for protection. They are also known for their adaptability, often thriving in a wide range of environments, from forests to urban areas. The genus includes several well-known species, such as the black garden ant (Lasius niger).