Paper engineering

Today's Guardian Country Diary describes an exploration of the nest that tree wasps built in our garden hedge.

Tree wasps Dolichovespula sylvestris have this distinctive little black spot in the centre of the clypeus (the central frontal facial plate), and a fine pair of jaws for catching prey and .........

... chewing fibres of rotten wood .

I suspect the wasp in this image is Vespula vulgaris.

They carry a ball of fibes away in their jaws and mix it with saliva. 

These three pictures show a red wasp Vespula rufa chewing fibes from a picnic table.

They use this material to build paper nests of exquisite beauty, lightness and remarkable strength. The queen, emerging from hibernation, starts the nest by building a downward-facing dome attached to a twig with a few breeding cells inside, where ....

.... she lays her first eggs that hatch into grubs, which she feeds with insect food until they hatch as adults.

Then these ever-growing ranks of workers construct the nest around her, enclosing tiers of breeding cells, with just a small entrance hole. Each strip of different coloured paper represents the work of a single wasp, with it's own predilection for the colour and source of wood fibres or hairs that it shaves from the surface of plants. The green patches on the nest above are constructed from hairs from the young twigs of the weeping pear tree in our garden.

This is this year's completed tree wasp nest, excised from the hedge after the wasps have abandoned it. As the nest grows it incorporates surrounding twigs, so the whole structure is very light and remarkably strong, considering the fragility of the components.

The view from underneath, where you can see how the exterior is constructed from successive paper layers ..

The entrance hole, a busy thoroughfare at the height of summer.

This year's nest had some red stripes in it, which I'm pretty sure came from the bark of a dead branch of a cypress tree in the garden.

One dead wasp guarded the entrance when I began to dissect the abandoned nest ....

....revealing the tiers of hexagonal breeding chambers inside ....

... and the multi- layered outer wall. When outdoor clothing companies advertise their cleverly designed products with layered insulation, remember that wasps invented this form of insulation millions of years ago!

These breeding chambers are built with astonishing precision by wasps working in total darkness, using wood fibre glued with saliva. Presumably they use the initial cells, built by the queen in daylight, as their template. Many of the cells on this nest contained grubs that died during development...... you can see one top centre in the above image.

 The grub weaves a white domed covering, that's opened by workers that come to feed it with chewed insects - and receive a sugary secretion that acts as their food in return for their efforts. This mutual dependence of grubs and adults ensures social cohesion in the colony.

The cells with the tattered white edges were homes to wasp grubs that developed successfully and chewed their way out at maturity.

Near the bottom of the nest I found these cells with dead grubs still sealed inside, almost on the point of hatching. One adult had begun to chew its way through the shroud but died in the attempt, never experiencing life beyond the darkness inside the nest. 

So near, yet so far .....

All the wasp-related info on this blog is collected here