10 May 2018

Pestwatch: Queen wasps

Technical | PPC91 May 2018

For our second in-depth PestWatch feature, Natalie and Dee are doffing their caps to the most regal of all the species you’re likely to encounter - the queen wasp.

A bit of biology queen wasps

Wasps are beneficial in gardens as they feed their grubs on caterpillars and other insects, thereby reducing these pest populations. Where possible it is worth leaving wasp nests to continue their valuable activities. However, there can come a time when the presence of wasps is detrimental to public health due to their sting and associated reactions such as anaphylactic shock and the pain caused by the stings. Fear can also play a part in needing to destroy a wasp nest but should only be done so in extreme circumstances. Education will mostly discourage treatments.

We also have that period before nests establish (Spring/early Summer) and when the nests wind down for the year (Autumn) when queen wasps cause a nuisance to householders and businesses across the UK. Pest controllers may often receive calls for ‘wasp nests’ which turn out to be a few ‘waking’ queens or queens seeking hibernation spots. The presence of these queens can cause concern among members of the public.

Life cycle of a Queen Wasp

Royal protocol: Dealing with queen wasps

As mentioned, in most circumstances pest controllers can recognise very quickly, just from the description from the customer, that a call for a ‘wasp nest’ is in fact queen wasps emerging from hibernation or seeking hibernation spots. Most of these call-outs can be ended by advising the customer that the queens will quickly move on and are generally harmless to humans and are very beneficial to the biodiversity.

Queen wasps get their sweet sugary liquids as nectar from flowers making them valuable pollinators. Many homeowners mistakenly assume that they must have a nest when queens emerge from their crevices in spring and sadly many use pesticides to kill off the queens. The best thing to do is open the windows and allow the queens to escape and then seal up entry points into the property from the outside to make it wasp proof, thereby preventing the problem the following year.

Where there may be a need to deal with large numbers of emerging queens, which is usually very rare, there are options for quick knockdowns in roof spaces. Always remember to read the product label and ensure there are no non-target animals present, for example, bats.

The Royal welcome: Emergence 

From as early as the beginning of March to as late as the end of May, when queen wasps come out of hibernation they have the important and time-consuming task of establishing their colony as quickly as possible. For queen wasps this is a deadly race against time which most of them will lose.

Not only do they have to find nectar to feed themselves but they also have to find a suitable nesting place and start building their nests. Queen wasps fly low to the ground, searching for any round, dark object or depression. If it is a hole, they fly in to see if it is suitable and if not, move on to the next hole. This can be a void, crack or crevice within buildings.

When a typical queen wasp has found a suitable site for nesting, thousands of trips are required to collect wood which she pulps into mulch to build the nest. The first thing the queen builds is the foundations of the nursery. Even before the nursery is complete, the queen will lay several eggs to bring on her brood as quickly as possible. She will then continue to build her nest and the nursery around her first eggs.

All adult wasps feed on sweet liquids that are packed with high energy sugars. However, this changes when the eggs hatch into grubs. The grubs need protein to grow so the queen changes her behaviour. At this point she starts to hunt for other insects to feed her brood.

With the queen hunting and collecting wood and building her nest, she has no time to feed herself. Nature extraordinarily deals with this problem. Insect skeletons are made from chitin. Chitin is a material made from densely packed and tightly bound sugars. When the grubs in the nest eat insects caught by the queen they convert the chitin into free sugars which they then refeed to the queen. This allows the queen to get on with her race to establish her colony without having to find food for herself.

When the nest is completed the queen is replaced by the workers as the foraging force and instead is now concerned only with nursing and egg producing. Her ovaries develop, abdomen becomes distended with eggs and hence she loses the ability to fly.

Royal succession: Hibernation

After the establishment phase has been completed, the colony encounters a change where the workers begin to build queen cells. Once the workers start building the queen cells, no more worker cells are built but those that still have brood growing in them are retained. The majority of the food resources brought in by the workers are fed to the queen larvae, and the lack of feeding for other larvae causes the prolongation of their larval periods.

When the queen has completed her job of producing queen larvae she dies, leaving a crop of virgin queens which will leave the nest, mate, hibernate and reproduce in the following Spring.

Only sexually-mated queens overwinter by hibernating. Many virgin queen wasps will not make it to the hibernation stage as if they fail to be fertilised then they will simply die off with the remaining worker force. It is thought that the stronger queens are judged this way by size and therefore also fat content, and so will be chosen for fertilisation ready for hibernation. The weaker queen wasps will most likely be unsuccessful, and so die.

Queens will hibernate in crevices and sheltered places but a lot will not survive as spiders are responsible for killing a large number of queens because they share the same crevices and sheltered spaces. Warm winters also kill large numbers of queens.

Cold, harsh winters are good for wasp populations. Mild or warm winters see queen wasps coming out of hibernation too early. Early emergence means there isn’t enough nectar available because plants aren’t in flower and small insects will also be less abundant. As a consequence, large numbers of queen wasps die from starvation.

With long, harsh winters, queens stay asleep until plants start to flower when there is ample nectar to support them, as well as the much-needed protein of small insects and aphids for the growing legless grubs (larvae). Overwintering queen wasps emerge from hibernation when temperatures in the shade reach about 10°C.

Did you know about wasps

  • Wasps make up an enormously diverse array of insects, with some 30,000 identified species
  • Most wasps are solitary, non-stinging varieties
  • Wasps are on every continent except Antarctica
  • A social wasp in distress emits a pheromone that sends nearby colony members into a defensive, stinging frenzy
  • Only females have stingers as these are really modified egg-laying organs

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Natalie and DeeDee Ward-Thompson and Natalie Bungay
BPCA Technical Team

1 May 2018  |  PPC91

Source: PPC91

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