What is the primary characteristic of bald-faced hornets' nests?

The primary characteristic of bald-faced hornets' nests is that they create large gray nests often found in trees or under eaves. These nests are distinctive due to their paper-like structure, which is created from chewed wood fibers mixed with saliva. This building process results in a robust and typically spherical nest that can be significantly large compared to the nests of many other insect species. Their placement high up in trees or on the sides of buildings also makes them relatively prominent, allowing for easier identification. The gray coloration of these nests further contributes to their characteristic appearance, distinguishing them from the nests of other wasp species, which may vary in size and color.