Left: Paper wasp nest (probably Vespula vulgaris). Right: Hornet workers emerging from their nest behind an air brick
The year for social wasps starts during the spring when fertile female wasps and hornets emerge from the sheltered places where they have overwintered. These are queens that will search for suitable locations where they can begin to build their nests. Initially the queen is on her own and has to feed herself and gather wood fibres to construct the first phase of her nest. This starter nest is not much bigger than a golf ball. It contains a small comb within an outer envelope, with about half a dozen cells where the queen lays fertilised eggs and raises her first brood of larvae. These will become worker wasps, which are infertile females. As the number of worker wasps increases, they can take over the food gathering and nest building activities, allowing the queen to remain in the nest and concentrate on laying eggs.
When at peak strength in mid-late summer, a nest can contain more than a thousand adult wasps. At that time the queen will lay some unfertilised eggs. Larvae from those eggs will become male wasps. Some of the larvae from fertilised eggs will be given additional food as larvae and this allows them to become queen wasps with functional ovaries. Mating takes place outside of the nest.
The old queen’s egg-laying begins to tail off, signalling the decline and end of the colony. Nests of Dolichovespula species usually die out in late summer, while those of Vespula species and the hornet can persist into late autumn. At the end of the season, the old queen, males and workers all die. Only the young queens overwinter. They leave the old nest and seek shelter in places such as in outbuildings, under loose bark and in dense conifer hedges.
The exception to the above is the Cuckoo wasp, Vespula austriaca. Overwintered queens of the Cuckoo wasp are unable to initiate nests of their own. They seek out and enter established nests of the Red wasp, Vespula rufa. The Red wasp queen is killed and the colony is taken over by the Cuckoo wasp queen. The eggs she lays are all destined to become males or young queens. She has no need to produce worker wasps of her own as her larvae will be fed by the Red wasp workers.
Role of social wasps in gardens
Wasps and hornets are generally beneficial by feeding their larvae on other insects, some of which may be pests of garden plants. Queen wasps visit flowers in spring to feed on nectar and the workers and males often do so in late summer-autumn. Like other flower-visiting insects, they can transfer pollen between plants and bring about pollination.
Wasps can also be a nuisance, largely because of their attention to sweet substances in late summer. They will feed on ripening fruits and cause annoyance at picnics and barbeques. Worker wasps can inflict painful stings but generally only do so in defence of themselves or their nests. Wasp and hornet nests sometimes need to be destroyed but they should be tolerated where they do not pose a risk to people.
If the Asian hornet does become established in Britain, it will be a more significant problem. It preys almost entirely on honeybees, particularly targeting bees as they leave or enter their hives. This makes honeybees reluctant to go out to forage, which has an impact on pollination and honey production. Weakened beehives will be invaded by Asian hornets, which kill the adult bees and carry off the larvae and pupae as food for the hornet larvae.
Other sources of information
Edwards, R. (1980) Social wasps – their biology and control. Rentokil Library
Social Wasps Field Guide sheet (1997) Peregrine Productions.