English: Wasps' nests at the Natural History Museum in London, England: Polybia scutellaris from south-east Brazil, Chartergus metanotalis from north-west Brazil and Pseudopolybia compressa from Brazil. These wasps' nests are all made of paper. The wasps chew plant fibres into a pulp, mixing it with their sticky saliva to make a lightweight, waterproof building material. An outer casing protects layers of hexagonal cells where eggs and young wasps develop. The entrances are small and easily guarded against predators. Solitary wasps' nests may be as simple as a burrow in the soil. But social wasps, which often live in colonies of thousands, are more ambitious. Their nests vary in shape and size from one type of wasp to another as you can see from these three examples.