Closeup of a wasp's nest

This is about 10cm x 10cm in actual size. It is part of the outside of a large (human-head-size) wasp's nest under our stairs, dormant now (do they come back or only use it once?)

I have no idea how the pattern is made. The material is apparently a paper made from pulp produced by masticating rotten wood.

A document by Downing and Jeanne says "[The paper] wasp uses other additional types of cues and evaluates some of the same nest features at each step of construction. Thus, this wasp is able to analyse many different aspects of its nest at one time to determine the correct building sequence and methods, a process more complex than that proposed by stigmergy theory."

Stigmergy theory says, basically, that what gets built depends on what's already there: Complexity arises in stigmergic systems because individuals interact not with each other but with a common environment. They interact with the environment by making changes to it. These changes affect the the way further changes are made. This gives rise to a positive feedback effect, where information feeds upon information (much the same effect as when conversations can take unpredictable directions according to the way people respond to each other's comments). See this article.