Which type of wasp makes a nest which has a single circular layer of hexagonal cells?

The type of wasp that constructs a nest characterized by a single circular layer of hexagonal cells is indeed the paper or umbrella wasp. These wasps typically build their nests using a papery substance that they create by chewing wood fibers mixed with their saliva. The nests are often distinctive in shape, resembling an umbrella, and contain a series of hexagonal cells that are arranged in a single layer, which serves as individual chambers for raising their young.

This nesting behavior is particularly different from other wasps. For example, yellowjackets and bald-faced hornets build more complex nests that are often larger and may consist of multiple layers and more elaborate structures. Understanding the unique features of each wasp's nest can help in identifying them and understanding their behavior within the ecosystem. The straightforward design of the paper or umbrella wasp nests allows them to be easier to spot when observing wasp activity in nature.