By the end of the summer, the workers in a wasp nest will have finished raising and feeding the new queen larvae. The larvae have spun caps over their cells and begun the process of pupation. This indicates a change for the nest.
The old queen wasp, at this stage, stops producing eggs and soon there will be no more larvae. This is a problem for the worker wasps: they hunt protein, usually invertebrates, to feed to the growing larvae but forage for carbohydrates for themselves and for their queen. But these carbohydrates, nectar and honeydew, are not anywhere near the whole of their diet; the larvae reward the workers for their protein meals by producing a sugar rich excreta, believed to contain essential nutrients, which the workers drink.
Worker wasp and capped larval cells; worker wasp feeding on grapes
A mature nest, after the new queens and the males have left and the old queen has died, is one in which there are a large number of adult wasps but few, if any, larvae. The wasps, without the larvae’s sugar solution contributing to their diet, go hungry. The nest’s social order begins to break down and the workers might abandon or kill the remaining larvae or take to cannibalism.
The most visible outcome, though, is lots of starving wasps hunting in our picnics and barbecues for liquid sugar. They drown themselves in soft drink cans on garden tables, walk over the jam on our toast, get drunk on the sugars of rotting fruit and are generally a nuisance. People get stung.
Common wasp (Vespula vulgaris) and a common wasp queen, newly emerged from hibernation in the spring, feeding on aphid honeydew
We think of it as the wasp time of year but the wasps have quietly been getting on with their business all through the summer. Their usual business is conducted out of our sight and often to our benefit because they hunt the sort of invertebrates we consider pests. The wasp in our beer, in September, is dying of starvation; the whole nest is dying.
Only the newly mated queens, whose hatching signalled the end of the colony, will survive the winter.