Few things ruin a summer barbecue faster than the common wasp (Vespula vulgaris). Their persistent nature and painful sting has earned them status as the ‘gangsters of the insect world’, causing panic and fear in public eyes. They are social insects forming colonies inside nests in soil banks, roof spaces, cavities, tree trunks, flowerbeds and walls. In rare cases a single sting can result in anaphylactic shock which can be fatal at short notice without medical attention.
The biology and lifecycle of the wasp is fascinating. Urban environments offer plenty of prime real-estate for hibernation bringing wasps and humans in close contact many times throughout the coming year. Queens emerge in mid-April to form a new colony. Once a suitable nest is located, queens will begin stripping wood and chewing it into a paper-like substance with which they build their nest.
Within individual chambers, the queen lays 10-20 eggs feeding the resulting larvae after a week on insect and invertebrates. The emergent first generation of workers (sterile males) takes over the role of providing food for subsequent eggs. As the colony grows the roles of hunting, brood care and nest construction are delegated to adult offspring workers.
The nest continues to grow until late summer, up to three to five thousand individuals, with males and young queens emerging, mating occurs, and the fertilised queens fly away to select suitable overwintering sites. With Autumn approaching the queen stops producing offspring, the workers leave their responsibilities of foraging for prey and instead turn their attention to sugar, thus to prolong their own life, often bringing them in contact with humans.
The onset of winter weather kills of all workers and the remaining males with only the fertilised queens surviving in hibernation to start new colonies next Spring. Old nests are not re-used although in favourable sites a new nest may be built close to an old one.
Wasps are valuable predators in our ecosystem – eating pest species such as caterpillars, aphids and whiteflies which make up a sizeable proportion of common wasp’s diets – implicating the economic importance of wasps as biocontrol agents in assuring food security for our growing population. Without wasp’s we would certainly see a huge rise in various insect pests.
Wasps often end up transporting pollen between the plants they visit, pollinating various species encountered in the countryside e.g. figworts, ivy and thistles. Wasps are more abundant in degraded or fragmented habitats such as agricultural, commercial development, urban environments or water diversion and play an important back-up to other pollinators.
Most domestic type aerosol sprays based on pyrethrin’s/pyrethroids are not suitable for wasp control in view of their tendency to cause hyper-activity to wasps. Professional commercial products like bendiocarb dust formulations and residual concentrated sprays may be applied to entrance sites effectively.
Wasps acts as predators and pollinators benefitting the garden. Wasps only generally sting in defence of the nest. Potential threat to human health and safety results in occasional control of the species.
Mervyn WalshBA(Hons), HDip.EnvMgt, MRSPH
Field Conservation Biologist