The Mystery Of Disappearing Wasps
Where do wasps go in the winter?
Wasps, like all insects, are subject to a life cycle. The wasp nest has a life cycle all of its own that starts after a long winter sleep.
In the UK most wasp and hornets nests start and end in April and September. Start and end times vary depending on the weather and temperature.
In 2019 we enjoyed record temperatures meaning that many nests are still going strong well into November.
So you can see that nature uses it’s random, climatic opportunities to its advantage.
When Do Wasps Nests Mature?
Wasps like the median wasp have quite small colonies compared to the Common or European wasps. Once their nest reaches about the size of a football, nest construction stops, and the nest matures.
Once the nest hits that magic, unknown maturity peak, queens and males develop and leave the colony, signalling its demise.
This could be because the queen of the median wasp has a smaller number of fertile eggs.
Whatever the true reason, this species of wasp seems to have two or three broods a year but appears to be sensitive to the climate.
During 2010 these wasps were common, but early snow in December 2010 meant that in 2011 median wasps almost disappeared!
Do Wasps In Winter Die?
Common and European wasps have the capacity to produce massive nests supporting tens of thousands of workers. Even with considerable nests, the seasonal decline in prey and temperature, mean that UK wasps naturally die off.
In countries like New Zealand, the picture can be very, very different. Thomas (1960) discovered that the German wasp (Vespula germanica) colonies often overwintered. Warm winters and an abundance of prey ensure all-year-round viability of nests allowing nest population to spiral beyond 100000 insects.
These nests are significant both in scale and in the lethal potential such colonies pose to humans and animals alike.
British wasps have very harsh climatic changes to endure, compared to the same species in Australia and New Zealand.
The Wasps Nest Matures
As the year draws to a close the temperature and prevailing conditions begin to make a wasps life increasingly difficult, signalling the start of the nest’s wintery end.
As the nest matures and the queen stops laying her precious eggs, the remaining larvae become future males and queens.
The male wasps are often recognizable by their lack of a sting, elongated abdomen and far hairier appearance.
Late emerging males die shortly after mating and are a common sight indoors. Once again, cooler autumn conditions leave them wandering around the inside.
By contrast, the new queens continue to hunt for a short time before settling into a suitable hibernation site for the winter.
Queens that mature early in the year will go on to create new nests in the same calendar year and perish as winter tightens its grip. Queens that emerge late in the year prepare for their long winter hibernation.
As seen in the image below, the queen wasp will settle down into hibernation, with her wings set tight to her body.
Do Winter Wasps Hibernate In Houses?
Yes. Wasps regularly hibernate in houses and homes of all kinds. Checking your loft for overwintering wasps in March and March can help you avoid a new nest in the coming year.
Popular nest sites include sheds, garages, extension roofs, lofts and attics, woodpiles, rodent burrows and many more.
Wasps In The Autumn
What we regularly encounter between September and December is the phenomena of wasps entering homes from beneath floors. Wasps enter through holes in walls and ceilings and also down chimneys.
As temperatures fall below 10°C the wasps remaining in the nest at the end of the year become increasingly disorientated. The effect of cold wintery conditions on the wasps central nervous system is similar to that of hypothermia in humans.
A reduction of available food from both external sources (insects and fruit) and internal sources (larvae) in the colony further reduces coordination as the nest steadily declines towards death.
All in all, they experience something of a famine. This causes them to wander into areas of a property where they would otherwise have no reason too.
As the days grow shorter, it becomes more likely that wasps will explore the cavity in which they nested.
Wandering wasps, in search of an exit into warm sunshine often discover its actually a light-bulb in someone’s bedroom.
In the UK, the wasp control season begins in April/May and runs until wasp activity ends in the Autumn. This means most pest controllers are very switched on to wasp activity from one year to the next.
The busiest months for control are June, July and August. As nests mature, wasps become more aggressive and unpredictable.
The danger for wasps is a mild autumn in which we have a sudden fall in temperatures. This can wipe out a large proportion of wasps before they have the chance to hibernate. A catastrophic event.
Thomas, C. R. 1960: The European wasp (Vespula germanica Fab.) in New Zealand. New Zealand Department of Scientific and Industrial Research,
information series no. 27: 74 p.